CN102497557B - Image compression and decompression method and system based on 2x2 coding unit - Google Patents

Abstract

The invention provides a fixed compression ratio image compression method based on a 2x2 coding unit, which is used for coding a 2x2 coding unit in an image, the compression method firstly judges whether the 2x2 coding unit is one of a first artificial type, a second artificial type and a third artificial type, if so, the coding unit is judged to be the 2x2 coding unit of the artificial type, otherwise, the coding unit is judged to be the 2x2 coding unit of the natural type, then the 2x2 coding unit of the artificial type is subjected to differential error coding, quantization and table look-up coding to generate first coding data, or the 2x2 coding unit of the natural type is subjected to color gamut conversion to obtain a 2x2 color gamut conversion unit, then the 2x2 color gamut conversion unit is subjected to discrete cosine conversion to generate a 2x2 frequency domain unit, and finally the 2x2 frequency domain unit is subjected to quantization and table look-up coding to generate second coding data.

Description

Image compression and decompression method and system based on 2x2 coding unit

technical field

The invention belongs to the technical field of image compression and decompression, in particular to a fixed compression rate image compression and decompression method and system based on 2x2 coding units.

Background technique

As we all know, lossless image compression technology can be divided into: run length (Run Length) coding, Huffman coding (Huffman Coding), Lempel-Ziv-Weich coding, arithmetic coding (Arithmetic Coding), differential coding (Differential Coding) and lossless JPEG coding (Lossless JPEG), etc. Among them, Run Length encoding is to change a series of the same data into two bytes (Byte) to represent, the previous byte (Byte) is the length of the string of data (that is, the number of repetitions), and the next byte (Byte) are used to record data. For example, a piece of data is "555555AA", which becomes "652A" after being encoded by Run Length, which means that there are 6 "5" and 2 "A", and this compression method saves 4 bytes of space. However, Run Length encoding needs to count the repetition rate of the input data. When the repetition rate of the data is low, the compression ratio is also reduced.

Huffman coding is to encode the input data according to the probability of occurrence using a binary tree (Binary Tree). Symbols with a high probability of occurrence are represented by a code with a shorter length, and symbols with a small probability of occurrence are represented by a code with a longer length. Therefore, the average The amount of data used is small, however, it is the same as the Run Length encoding, and it needs to count the probability of the input data appearing.

Lempel-Ziv-Weich encoding uses the existing strings as the basis for index lookup table comparison, and the way of indexing is used as a data compression stream. However, the Lempel-Ziv-Weich encoding method needs to use a large memory space to temporarily store the created table.

The biggest feature of Arithmetic Coding is that it does not use a symbol to represent a bit, but a real number to represent a compressed string. This method needs to read the original string first, count the occurrence probability of each different character code, divide the 0 to 1 real number interval into the original code interval table according to this probability, and then read the characters of the original string one by one, Every time a character is read, the interval occupied by it will be divided by the original encoding interval table, so that after the last character is read, a final interval will be generated, and then a real number will be selected from this interval to represent the compressed file of the original string . The code obtained by arithmetic coding only needs a space to store floating-point numbers, and does not need a large amount of space to store like Huffman coding. However, its disadvantage is that it needs to count the probability of occurrence of input data and the algorithm is very complicated.

Differential encoding uses the difference between the estimated value and the actual value as the basis for compression, and the compression rate is low when it is used alone. Lossless JPEG encoding uses discrete cosine transform and estimated error value as the basis for compression.

In the aforementioned compression methods, the compression rate is not fixed, and more computing resources are often required during decompression to obtain the data length correctly. At the same time, in an embedded system or handheld device, due to its limited computing power And limited memory capacity, the above image compression techniques are difficult to use in embedded systems or handheld devices. It can be seen that there is still room for improvement in the image compression and decompression functions on embedded systems or handheld devices.

Contents of the invention

The purpose of the present invention is to provide a method and system for image compression and decompression with a fixed compression rate based on 2x2 coding units, so as to generate an image with a fixed compression rate, reduce hardware requirements and maintain image quality at the same time.

According to a characteristic of the present invention, the present invention proposes a fixed compression rate image compression method based on 2x2 coding units, which encodes a 2x2 coding unit of an image, the image has at least one 2x2 coding unit, and the image compression method The method comprises the following steps: (A) receiving a 2x2 coding unit, which includes upper left corner pixels, upper right corner pixels, lower left corner pixels and lower right corner pixels arranged in a matrix; (B) judging whether the 2x2 coding unit is the first artificial type to One of the seventh artificial types, if so, then determine that the 2x2 coding unit is a 2x2 coding unit of an artificial type, otherwise, determine that this 2x2 coding unit is a 2x2 coding unit of a natural type, wherein the first artificial type is the four The pixels are two horizontal stripes in the horizontal direction, the second artificial type is two vertical stripes in the vertical direction for the four pixels, the third artificial type is the intersection of two oblique stripes in the direction of the four pixels at an angle of 45 degrees, and the fourth To the seventh artificial type, the four pixels are a combination of a triangle and a single point; (C) differential error encoding, quantization, and table look-up encoding are performed on the 2x2 coding unit determined to be an artificial type to generate the first encoded data; (D ) performing color gamut conversion on a 2x2 coding unit determined to be a natural type to obtain a 2x2 color gamut conversion unit; (E) performing discrete cosine transform on the 2x2 color gamut conversion unit to generate a 2x2 frequency domain unit; and (F) Quantization and table look-up coding are performed on the 2x2 frequency domain unit to generate second coded data.

According to another characteristic of the present invention, the present invention proposes a fixed compression rate image decompression method based on 2x2 coding units, the method is to decode a coded packet of a fixed bit size to generate a 2x2 decoding unit of an image , the 2x2 decoding unit includes four pixels arranged in a matrix, the image has at least one 2x2 decoding unit, and the image decompression method includes the following steps: (A) receiving an encoded packet; (B) a main packet according to the encoded packet Header (1 bit, 1 bit) judges whether this coding packet is artificial type, if so, then judges that this coding packet is the coding packet of artificial type, otherwise, judges that this coding packet is the coding packet of natural type; (C) Carrying out dequantization, anti-lookup table decoding and anti-differential error decoding on the artificial type encoded packet to generate the first decoded data; (D) dequantizing and anti-lookup table decoded on the natural type encoded packet to generate the second decoding data; (E) performing discrete cosine transform on the second decoded data to generate third decoded data; (F) performing color gamut conversion on the third decoded data to obtain fourth decoded data; and (G) receiving the the first decoded data or the fourth decoded data, and reconstruct the first decoded data or the fourth decoded data to generate a 2x2 decoding unit.

According to another characteristic of the present invention, the present invention proposes a display system with a fixed compression rate based on 2x2 coding units, which compresses and decompresses a display image. The display system includes a display module, an image input device, A fixed compression rate image compression device based on 2x2 coding units, a temporary storage device, a fixed compression rate image decompression device based on 2x2 coding units, and a timing controller connected to the fixed compression rate image based on 2x2 coding units The decompression device receives the 2x2 decoding unit to generate the timing driving signal and display data of the display module. The display module is used for displaying an image. The image input device is used for inputting a display image. The fixed compression rate image compression device based on 2x2 coding units is connected to the image input device, and encodes the 2x2 coding units of the display image to generate a coded packet corresponding to the 2x2 coding units, wherein the image has at least one 2x2 coding unit. The temporary storage device is connected to the fixed compression rate image compression device based on 2x2 coding units to temporarily store the encoded packets output by the fixed compression rate image compression device based on 2x2 coding units. The fixed compression rate image decompression device based on 2x2 coding unit is connected to the temporary storage device, receives the coded packet, and decompresses the coded packet to generate a 2x2 decoding unit corresponding to the 2x2 coding unit. The timing controller is connected to a fixed compression ratio image decompression device based on a 2x2 decoding unit, receives the 2x2 decoding unit, and generates timing driving signals and display data of the display module. Wherein, the fixed compression rate image compression device first judges whether the 2x2 coding unit is artificial or natural, so as to perform differential error coding, quantization and table look-up coding on the artificial 2x2 coding unit to generate a first coded data, and perform color gamut conversion, discrete cosine transform, quantization and look-up table encoding on the 2x2 coding unit of natural type, and then generate second encoded data, and then encapsulate the first encoded data or the second encoded data to generate fixed compression Rate encoded packets.

Description of drawings

Fig. 1 is a flow chart of a fixed compression rate image compression method based on 2x2 coding units of the present invention;

FIG. 2 is a schematic diagram of the image and 2x2 coding units;

Fig. 3 is the schematic diagram of man-made type and natural type among the present invention;

4 is a schematic diagram of differential error coding, quantization and table look-up coding of a 2x2 coding unit in Embodiment 1 of the present invention;

Fig. 5 is a schematic diagram of coding when the 2x2 coding unit is the first, second and third artificial types in Embodiment 1 of the present invention;

Fig. 6 is a schematic diagram of coding when the 2x2 coding unit is the fourth, fifth, sixth and seventh artificial types in Embodiment 1 of the present invention;

Fig. 7 is a schematic diagram of color gamut conversion and discrete cosine conversion in the present invention;

Fig. 8 is a schematic diagram of the extended man-made type in the present invention;

Fig. 9 is a schematic diagram of the differential error coding, quantization and table look-up coding of the extended artificial type in the first embodiment;

Fig. 10 is a schematic diagram of encoding when the 2x2 coding unit of the extended artificial type is the first, second and third artificial types in the first embodiment;

Fig. 11 is a schematic diagram of encoding when the 2x2 coding unit of the extended artificial type is the fourth to seventh artificial types in the first embodiment;

Fig. 12 is a schematic diagram of encoding when the 2x2 coding unit of the extended artificial type is the eighth to the thirteenth artificial type in the first embodiment;

FIG. 13 is a schematic diagram of natural type encoding in Embodiment 1;

Fig. 14 is a schematic diagram of a table lookup operation of a natural type in Embodiment 1;

Fig. 15 is a schematic diagram of differential error coding, quantization and table look-up coding of the extended artificial type in the second embodiment;

Fig. 16 is a schematic diagram of encoding when the 2x2 coding unit of the extended artificial type is the first, second and third artificial types in the second embodiment;

Fig. 17 is a schematic diagram of encoding when the 2x2 coding unit of the extended artificial type is the fourth to seventh artificial types in the second embodiment;

Fig. 18 is a schematic diagram of encoding when the 2x2 coding unit of the extended artificial type is the eighth to the thirteenth artificial type in the second embodiment;

Fig. 19 is a schematic diagram of the encoding of the natural type in the second embodiment;

Fig. 20 is a schematic diagram of a table lookup operation of a natural type in Embodiment 2;

Fig. 21 is a flowchart of an image decompression method with a fixed compression rate based on 2x2 coding units of the present invention;

FIG. 22 is a structural diagram of a display system applying a fixed compression rate based on 2x2 coding units according to the present invention.

In the accompanying drawings, the parts represented by each label are as follows:

S110～S180, steps,

210, image, 220, 2x2 coding unit,

310, the first artificial type, 320, the second artificial type, 330, the third artificial type, 340, the fourth artificial type, 350, the fifth artificial type, 360, the sixth artificial type, 370, the seventh artificial type, 380 , first natural type, 390, second natural type,

700, 2x2 color gamut conversion unit, 710, brightness 2x2 color gamut conversion unit, 720, first chroma 2x2 color gamut conversion unit, 730, second chroma 2x2 color gamut conversion unit, 750, 2x2 frequency domain unit, 760 , Brightness 2x2 frequency domain unit, 770, first chroma 2x2 frequency domain unit, 780, second chroma 2x2 frequency domain unit,

S805～S850, steps,

900. Display system, 910. Display module, 920. Image input device, 930. Fixed compression rate image compression device based on 2x2 coding unit, 940. Temporary storage device, 950. Fixed compression rate image decompression device based on 2x2 coding unit , 960, timing controller, 970, source driver, 980, gate driver

Detailed ways

In order to make the object, technical solution and advantages of the present invention clearer, the present invention will be further described in detail below with reference to the accompanying drawings and examples.

FIG. 1 is a flow chart of a fixed compression rate image compression method based on 2x2 CUs according to the present invention, which encodes one 2x2 CU in an image.

First, in step S110, the image compression method receives a 2x2 coding unit, and the 2x2 coding unit includes upper-left pixels, upper-right pixels, lower-left pixels, and lower-right pixels arranged in a matrix.

FIG. 2 is a schematic diagram of the image and the 2x2 coding unit. As shown in FIG. 2, the image 210 has at least one 2x2 coding unit 220, and each 2x2 coding unit 220 has four pixels A, B, C, and D, wherein, A is the upper left pixel, B is the upper right pixel, C is the lower left pixel, and D is the lower right pixel. Each pixel has three colors: red (r), blue (g), and green (b), where A _r , A _g , and A _b are the red, green, and blue values of pixel A, and B _r , B _g , B _b is the red value, green value, and blue value of pixel B; C _r , C _g , C _b are the red value, green value, and blue value of pixel C; D _r , D _g , D _b are pixel D Red value, green value, blue value of . Each color value can be selected to be 8 bits, so the 2x2 coding unit 220 has 96 (=4*3*8) bits. It is also possible to select 6 bits for each color value, so the 2x2 coding unit 220 has 72 (=6*3*4) bits.

In step S120, it is judged whether the 2x2 coding unit 220 is a man-made type, if so, it is determined that the 2x2 coding unit is a 2x2 coding unit of a man-made type, otherwise, it is judged that the 2x2 coding unit is a 2x2 coding unit of a natural type, wherein the man-made There are seven types of shapes, including: the first man-made type: four pixels form two horizontal stripes in the horizontal direction; the second man-made type: four pixels form two vertical stripes in the vertical direction; the third man-made type: four pixels form a 45 The two oblique stripes cross in the direction of the degree angle; the fourth to seventh man-made types: the four pixels are a combination of triangles and single points.

To further illustrate, in step S120, it is first judged whether the 2x2 encoding unit 220 is one of the first artificial type to the third artificial type, and then it is judged whether the 2x2 encoding unit 220 is the fourth artificial type to the seventh artificial type one of the.

Fig. 3 is a schematic diagram of the artificial type and the natural type of the present invention. The classification of the first artificial type to the seventh artificial type in the present invention helps to deal with specific patterns such as font edges, grayscale changes, jagged, checkerboard, etc., and the packet recording method of the present invention can make these coding units achieve distortion-free .

As shown in FIG. 3 , the first artificial type 310 is two horizontal stripes in the horizontal direction of the four pixels, that is, the color value (X) of pixel A is the same or similar to the color value (X) of pixel B, and the color value (X) of pixel C is the same as or similar to that of pixel B. The color value (Y) is the same or similar to the color value (Y) of the pixel D. Similarly, the second artificial type 320 is two vertical stripes in the vertical direction of the four pixels, the third artificial type 330 is the intersection of two oblique stripes in the direction of the four pixels at an angle of 45 degrees, and the fourth artificial type 340 , the fifth artificial type 350 , the sixth artificial type 360 and the seventh artificial type 370 are combinations of the four pixels in a triangle shape and a single point. That is: the first artificial type 310 is the approximation (X) of the upper left pixel and the upper right pixel and the approximation (Y) of the lower left pixel and the lower right pixel; the second artificial type 320 is the approximation of the upper left pixel and the lower left pixel (X) and the upper right pixel and the lower right pixel are approximate (Y); the third artificial type 330 is that the upper left pixel and the lower right pixel are approximate (X) and the lower left pixel and the upper right pixel are approximate (Y); the fourth The artificial type 340 is the approximate (Y) of the lower left pixel, the upper right pixel and the lower right pixel; the fifth artificial type 350 is the approximate (Y) of the upper left pixel, the upper right pixel and the lower right pixel; the sixth artificial type 360 is the approximation (Y) of the upper left pixel, lower left pixel and upper right pixel; the seventh artificial type 370 is the approximation (Y) of the upper left pixel, lower left pixel and lower right pixel.

In step S120, when the following formula is satisfied, it is determined that the 2x2 encoding unit 220 is the first artificial type 310:

ABS(A _r , B _r )<THD1, ABS(C _r , D _r )<THD1,

ABS(A _g , B _g )<THD1, ABS(C _g , D _g )<THD1,

ABS(A _b , B _b )<THD1, ABS(C _b , D _b )<THD1,

ABS(A _r ，B _r )+ABS(A _g ，B _g )+ABS(A _b ，B _b )≤

ABS(A _r ,C _r )+ABS(A _g ,C _g )+ABS(A _b ,C _b ),

ABS(A _r ，B _r )+ABS(A _g ，B _g )+ABS(A _b ，B _b )≤

ABS(D _r ，B _r )+ABS(D _g ，B _g )+ABS(D _b ，B _b ),

ABS(C _r ，D _r )+ABS(C _g ，D _g )+ABS(C _b ，D _b )≤

ABS(D _r ，B _r )+ABS(D _g ，B _g )+ABS(D _b ，B _b ),

ABS(C _r ，D _r )+ABS(C _g ，D _g )+ABS(C _b ，D _b )≤

ABS(A _r ,C _r )+ABS(A _g ,C _g )+ABS(A _b ,C _b ),

Wherein, THD1 is the first threshold value (its value is selected by those skilled in the art based on experience), A is the pixel in the upper left corner, B is the pixel in the upper right corner, C is the pixel in the lower left corner, and D is the pixel in the upper left corner. For the lower right pixel, Ar _r , A _g , A _b are the red value, green value and blue value of pixel A respectively, B _r , B _g , B _b are the red value, green value and blue value of pixel B respectively, _Cr , C _g , and C _b are red, green, and blue values of pixel C, respectively, and D _r , D _g , and D _b are red, green, and blue values of pixel D, respectively. Wherein ABS is the absolute value function of the difference between the two elements in the brackets, that is, when a≥b, ABS(a, b)=ab, when a<b, ABS(b, a)=ba.

In step S120, when the following formula is met, it is determined that the 2x2 encoding unit 220 is the second artificial type 320:

ABS(A _r , C _r )<THD1, ABS(B _r , D _r )<THD1,

ABS(A _g , C _g )<THD1, ABS(B _g , D _g )<THD1,

ABS(A _b , C _b )<THD1, ABS(B _b , D _b )<THD1,

ABS(A _r ,C _r )+ABS(A _g ,C _g )+ABS(A _b ,C _b )≤

ABS(A _r ，B _r )+ABS(A _g ，B _g )+ABS(A _b ，B _b ),

ABS(A _r ,C _r )+ABS(A _g ,C _g )+ABS(A _b ,C _b )≤

ABS(D _r ,C _r )+ABS(D _g ,C _g )+ABS(D _b ,C _b ),

ABS(B _r ，D _r )+ABS(B _g ，D _g )+ABS(B _b ，D _b )≤

ABS(D _r ,C _r )+ABS(D _g ,C _g )+ABS(D _b ,C _b ),

ABS(B _r ，D _r )+ABS(B _g ，D _g )+ABS(B _b ，D _b )≤

ABS(A _r , B _r )+ABS(A _g , B _g )+ABS(A _b ,B _b ).

In step S120, when the following formula is met, it is determined that the 2x2 encoding unit 220 is the third artificial type 330:

ABS(A _r , D _r )<THD1, ABS(C _r , B _r )<THD1,

ABS(A _g , D _g )<THD1, ABS(C _g , B _g )<THD1,

ABS(A _b , D _b )<THD1, ABS(C _b , B _b )<THD1,

ABS(A _r ，D _r )+ABS(A _g ，D _g )+ABS(A _b ，D _b )≤

ABS(A _r ，B _r )+ABS(A _g ，B _g )+ABS(A _b ，B _b ),

ABS(A _r ，D _r )+ABS(A _g ，D _g )+ABS(A _b ，D _b )≤

ABS(D _r ,C _r )+ABS(D _g ,C _g )+ABS(D _b ,C _b ),

ABS(C _r ，B _r )+ABS(C _g ，B _g )+ABS(C _b ，B _b )≤

ABS(D _r ,C _r )+ABS(D _g ,C _g )+ABS(D _b ,C _b ),

ABS(C _r ，B _r )+ABS(C _g ，B _g )+ABS(C _b ，B _b )≤

ABS(A _r , B _r )+ABS(A _g , B _g )+ABS(A _b ,B _b ).

In step S120, when the following formula is satisfied, it is determined that the 2x2 encoding unit 220 is the fourth artificial type 340:

ABS(B _r , D _r )<THD2, ABS(C _r , D _r )<THD2,

ABS(B _g , D _g )<THD2, ABS(C _g , D _g )<THD2,

ABS(B _b , D _b )<THD2, ABS(C _b , D _b )<THD2,

ABS(B _r ，D _r )+ABS(B _g ，D _g )+ABS(B _b ，D _b )≤

ABS(A _r ,C _r )+ABS(A _g ,C _g )+ABS(A _b ,C _b ),

ABS(B _r ，D _r )+ABS(B _g ，D _g )+ABS(B _b ，D _b )≤

ABS(A _r ，B _r )+ABS(A _g ，B _g )+ABS(A _b ，B _b ),

ABS(C _r ，D _r )+ABS(C _g ，D _g )+ABS(C _b ，D _b )≤

ABS(A _r ，B _r )+ABS(A _g ，B _g )+ABS(A _b ，B _b ),

ABS(C _r ，D _r )+ABS(C _g ，D _g )+ABS(C _b ，D _b )≤

ABS(A _r , C _r )+ABS(A _g , C _g )+ABS(A _b ,C _b ).

Wherein, THD2 is the second threshold value (its value is selected by those skilled in the art based on experience),

In step S120, when the following formula is satisfied, it is determined that the 2x2 encoding unit 220 is the fifth artificial type 350:

ABS(B _r , D _r )<THD2, ABS(A _r , B _r )<THD2,

ABS(B _g , D _g )<THD2, ABS(A _g , B _g )<THD2,

ABS(B _b , D _b )<THD2, ABS(A _b , B _b )<THD2,

ABS(B _r ，D _r )+ABS(B _g ，D _g )+ABS(B _b ，D _b )≤

ABS(A _r ,C _r )+ABS(A _g ,C _g )+ABS(A _b ,C _b ),

ABS(B _r ，D _r )+ABS(B _g ，D _g )+ABS(B _b ，D _b )≤

ABS(C _r ，D _r )+ABS(C _g ，D _g )+ABS(C _b ，D _b ),

ABS(A _r ，B _r )+ABS(A _g ，B _g )+ABS(A _b ，B _b )≤

ABS(C _r ，D _r )+ABS(C _g ，D _g )+ABS(C _b ，D _b ),

ABS(A _r ，B _r )+ABS(A _g ，B _g )+ABS(A _b ，B _b )≤

ABS(A _r , C _r )+ABS(A _g , C _g )+ABS(A _b ,C _b ).

In step S120, when the following formula is met, it is determined that the 2x2 encoding unit 220 is the sixth artificial type 360:

ABS(A _r , C _r )<THD2, ABS(A _r , B _r )<THD2,

ABS(A _g , C _g )<THD2, ABS(A _g , B _g )<THD2,

ABS(A _b , C _b )<THD2, ABS(A _b , B _b )<THD2,

ABS(A _r ,C _r )+ABS(A _g ,C _g )+ABS(A _b ,C _b )≤

ABS(B _r ，D _r )+ABS(B _g ，D _g )+ABS(B _b ，D _b ),

ABS(A _r ,C _r )+ABS(A _g ,C _g )+ABS(A _b ,C _b )≤

ABS(C _r ，D _r )+ABS(C _g ，D _g )+ABS(C _b ，D _b ),

ABS(A _r ，B _r )+ABS(A _g ，B _g )+ABS(A _b ，B _b )≤

ABS(C _r ，D _r )+ABS(C _g ，D _g )+ABS(C _b ，D _b ),

ABS(A _r ，B _r )+ABS(A _g ，B _g )+ABS(A _b ，B _b )≤

ABS(B _r , D _r )+ABS(B _g , D _g )+ABS(B _b ,D _b ).

In step S120, when the following formula is satisfied, it is determined that the 2x2 encoding unit 220 is the seventh artificial type 370:

ABS(A _r , C _r )<THD2, ABS(C _r , D _r )<THD2,

ABS(A _g , C _g )<THD2, ABS(C _g , D _g )<THD2,

ABS(A _b , C _b )<THD2, ABS(C _b , D _b )<THD2,

ABS(A _r ,C _r )+ABS(A _g ,C _g )+ABS(A _b ,C _b )≤

ABS(B _r ，D _r )+ABS(B _g ，D _g )+ABS(B _b ，D _b ),

ABS(A _r ,C _r )+ABS(A _g ,C _g )+ABS(A _b ,C _b )≤

ABS(A _r ，B _r )+ABS(A _g ，B _g )+ABS(A _b ，B _b ),

ABS(C _r ，D _r )+ABS(C _g ，D _y )+ABS(C _b ，D _b )≤

ABS(A _r ，B _r )+ABS(A _g ，B _g )+ABS(A _b ，B _b ),

ABS(C _r ，D _r )+ABS(C _g ，D _y )+ABS(C _b ，D _b )≤

ABS(B _r , D _r )+ABS(B _g , D _g )+ABS(B _b ,D _b ).

In step S130 , differential error coding, quantization and table look-up coding are performed on the artificial type 2×2 coding unit to generate first coded data.

In the 2x2 encoding unit, the three colors of red (r), blue (g) and green (b) of each pixel are respectively recorded in two specific embodiments using 8 bits and 6 bits to compress the image of the present invention. The method is described in detail.

Embodiment 1: the three colors of red (r), blue (g) and green (b) of each pixel in the 2x2 encoding unit are all recorded in 8 bits, so the 2x2 encoding unit 220 is 96 (=4×3× 8) bit.

Fig. 4 is a schematic diagram of differential error coding, quantization and table look-up coding of the 2x2 coding unit in Embodiment 1 of the present invention. In the first embodiment, each color value in the 2x2 coding unit 220 in Fig. 2 is represented by 8 bits In an embodiment, the 2x2 encoding unit 220 is 96 (=4×3×8) bits. In FIG. 4 , numbers represent the number of digits, for example, 8 and 7 represent 8 digits and 7 digits, respectively. A slash indicates a table lookup operation, and a backslash indicates a quantization operation.

In step S130, when the 2x2 encoding unit 220 is one of the first artificial type 310, the second artificial type 320 and the third artificial type 330, use 8 bits to record the average value of two pixels, and use 7 bits to record one The position of the 7-bit table, the record content of the 7-bit table position is: among all the recorded contents of the 7-bit table, the average value of the other two pixels in the 2x2 coding unit and the average value of the aforementioned two pixels recorded using 8 bits The value with the smallest difference. This form is a variable form and can be adjusted at any time. There are four tables in total: 7-digit table, 4-digit table, 3-digit table, and 2-digit table. The basic spirit: the value with a high probability of occurrence is built in the table, so it is easy to be selected. On the contrary, values with a small probability of occurrence are discarded and not created in the table, because the storage resources are limited (the size of the table is limited). The embodiment provided by the present invention is only one of the setting methods of a certain table. In fact, adjust the content of this form and the actual form of the product for subsequent optimization actions.

The first artificial type 310, the second artificial type 320 and the third artificial type 330 are all in the form of lines, so the first artificial type 310 is used as an illustration, and the second artificial type 320 and the third artificial type 330 are for those who are familiar with the technology What can be accomplished based on the technology of the present invention will not be repeated here.

Fig. 5 is a schematic diagram of encoding when the 2x2 encoding unit of Embodiment 1 of the present invention is the first artificial type, the second artificial type and the third artificial type, and the first embodiment is each of the 2x2 encoding units 220 in Fig. 2 In an embodiment where the color value is represented by 8 bits, the 2x2 coding unit 220 has 96 (=4*3*8) bits. It can be red, blue or green. First add the color value of pixel A (127) to the color value of pixel B (126), divide by 2 (126.5), and then round to get 127. Use 8 bits to record the value 127.

Add the color value of pixel C (34) to the color value of pixel D (32) and divide by 2 (33), round up to get 33, subtract the previously calculated value of 127 to get -94, although subtracting The result is 9 bits, but the present invention uses a 7-bit table for table lookup, which can reduce the amount of data generated after encoding. A 7-digit table is looked up according to -94. -94 is located between -95 and -90, and close to -95, so the position of -95 is obtained after looking up the table, and 7 bits are used to record the position of -95.

A total of 128 values are recorded in this 7-bit table. If -95 is closest to the jth value of the table, record "j". The "j" value can be calculated according to the following formula:

[a ₁ , a ₂ , a ₃ ,..., a _k-2 , a _k-1 , a _k ],

sign[α-a _j ]×sign[a _j+1 -α]≥0, (1)

Wherein, a ₁ to a _k are 128 values recorded in the 7-bit table, which are arranged in order from small to large. sign is a function that outputs the sign of the value, α is the value to be looked up in the table, once the formula (1) is satisfied, the j value is stored.

In step S130, when the 2x2 encoding unit 220 is one of the fourth artificial type 340, the fifth artificial type 350, the sixth artificial type 360 and the seventh artificial type 370, use 8 bits to record the average value, using 7 bits or 6 bits to record the quantized value of another pixel of the 2x2 coding unit 220.

The fourth artificial type 340, the fifth artificial type 350, the sixth artificial type 360, and the seventh artificial type 370 are all combinations of triangles and single points, so the fourth artificial type 340 is used as an example for illustration. The fifth artificial type 350, The sixth man-made type 360 and the seventh man-made type 370 can be accomplished by those who are familiar with the technology based on the technology of the present invention, and will not be repeated here.

Fig. 6 is a schematic diagram of encoding when the 2x2 coding unit of the first embodiment of the present invention is the fourth artificial type 340, the fifth artificial type 350, the sixth artificial type 360 and the seventh artificial type 370. In the embodiment in which each color value in the 2x2 encoding unit 220 is represented by 8 bits, the 2x2 encoding unit 220 has 96 (=4×3×8) bits. It can be red, blue, or green. It first adds the color value of pixel B (100), the color value of pixel C (100) and the color value of pixel D (100), divides by 3 to get 100, and then rounds to get 100, using 8 bits to record the value 100.

Quantize the color value (34) of pixel A, and then round off the decimal part to obtain the value 9, and use 6 bits to record the value 9. When the color of pixel A is green, the value 9 is recorded using 7 bits. This quantized operation is calculated by the following formula:

${\mathrm{<span\; class="notranslate">\; x</span>}}_{\mathrm{<span\; class="notranslate">\; Q</span>}}<span\; class="notranslate">\; =</span>\mathrm{<span\; class="notranslate">\; Round</span>}<span\; class="notranslate">\; (</span>\frac{\mathrm{<span\; class="notranslate">\; x</span>}}{\mathrm{<span\; class="notranslate">\; Q</span>}}<span\; class="notranslate">\; )</span>$

Among them, Q is a quantization factor, and Round is a rounding function. The quantization factor Q is 4 when 6-bit recording is used, and 2 when 7-bit recording is used.

When in step S120, it is determined that the 2x2 encoding unit 220 is not one of the first artificial type to the seventh artificial type, it means that the 2x2 encoding unit 220 is a natural type, so in step S140, the 2x2 encoding unit of the natural type The encoding unit 220 performs color gamut conversion to obtain a 2x2 color gamut conversion unit.

In step S140, a 2x2 color gamut conversion unit is obtained by performing RGB to YUV color gamut conversion, and the RGB to YUV color gamut conversion is performed by the following formula:

$\left[\begin{array}{c}\mathrm{<span\; class="notranslate">\; Y</span>}\\ \mathrm{<span\; class="notranslate">\; u</span>}\\ \mathrm{<span\; class="notranslate">\; V</span>}\end{array}\right]<span\; class="notranslate">\; =</span>\left[\begin{array}{ccc}\mathrm{<span\; class="notranslate">\; 0.25</span>}& \mathrm{<span\; class="notranslate">\; 0.5</span>}& \mathrm{<span\; class="notranslate">\; 0.25</span>}\\ <span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; 0.5</span>}& \mathrm{<span\; class="notranslate">\; 1</span>}<span\; class="notranslate">\; .</span><span\; class="notranslate">\; .</span>& <span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; 0.5</span>}\\ <span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; 1.0</span>}& \mathrm{<span\; class="notranslate">\; 0</span>}& \mathrm{<span\; class="notranslate">\; 1.0</span>}\end{array}\right]\left[\begin{array}{c}\mathrm{<span\; class="notranslate">\; r</span>}\\ \mathrm{<span\; class="notranslate">\; g</span>}\\ \mathrm{<span\; class="notranslate">\; b</span>}\end{array}\right]<span\; class="notranslate">\; ,</span>$

Among them, r represents the red value of a pixel, g is the green value of the pixel, b is the blue value of the pixel, Y is the brightness (Luminance, Luma) of the pixel, U and V are the chromaticity ( Chrominance). Fig. 7 is a schematic diagram of color gamut conversion and discrete cosine conversion of the present invention. As shown in Fig. 7, the 2x2 color gamut conversion unit 700 is respectively a brightness 2x2 color gamut conversion unit 710 and a first chroma 2x2 color gamut conversion unit 720 , and a second chroma 2×2 color gamut conversion unit 730 .

The values of the elements in the brightness 2x2 color gamut conversion unit 710 range from 0 to 255, and the values of the elements in the first chroma 2x2 color gamut conversion unit 720 and the second chroma 2x2 color gamut conversion unit 730 range from 0 to 255. -255～255, so the elements of the brightness 2x2 color gamut conversion unit 710 are 8 bits, the elements of the first chroma 2x2 color gamut conversion unit 720 and the second chroma 2x2 color gamut conversion unit 730 are 9 bits, and This is a calculation only and does not affect the final encoded bit count. Before proceeding to the next step S150 , the values of the elements of the brightness 2×2 color gamut conversion unit 710 need to be shifted from 0˜255 to −128˜127.

In step S150 , a discrete cosine transform is performed on the 2x2 color gamut conversion unit 700 to generate a 2x2 frequency domain unit.

In step S150, the discrete cosine transform is performed by the following formula:

$\left[\begin{array}{c}\mathrm{<span\; class="notranslate">\; E.</span>}\\ \mathrm{<span\; class="notranslate">\; f</span>}\\ \mathrm{<span\; class="notranslate">\; G</span>}\\ \mathrm{<span\; class="notranslate">\; h</span>}\end{array}\right]<span\; class="notranslate">\; =</span>\mathrm{<span\; class="notranslate">\; 0.25</span>}<span\; class="notranslate">\; \&times;</span>\left[\begin{array}{cccc}\mathrm{<span\; class="notranslate">\; 1</span>}& \mathrm{<span\; class="notranslate">\; 1</span>}& \mathrm{<span\; class="notranslate">\; 1</span>}& \mathrm{<span\; class="notranslate">\; 1</span>}\\ \mathrm{<span\; class="notranslate">\; 1</span>}& <span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; 1</span>}& \mathrm{<span\; class="notranslate">\; 1</span>}& <span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; 1</span>}\\ \mathrm{<span\; class="notranslate">\; 1</span>}& \mathrm{<span\; class="notranslate">\; 1</span>}& <span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; 1</span>}& <span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; 1</span>}\\ \mathrm{<span\; class="notranslate">\; 1</span>}& <span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; 1</span>}& <span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; 1</span>}& \mathrm{<span\; class="notranslate">\; 1</span>}\end{array}\right]\left[\begin{array}{c}\stackrel{<span\; class="notranslate">\; \&OverBar;</span>}{\mathrm{<span\; class="notranslate">\; A</span>}}\\ \stackrel{<span\; class="notranslate">\; \&OverBar;</span>}{\mathrm{<span\; class="notranslate">\; B</span>}}\\ \stackrel{<span\; class="notranslate">\; \&OverBar;</span>}{\mathrm{<span\; class="notranslate">\; C</span>}}\\ \stackrel{<span\; class="notranslate">\; \&OverBar;</span>}{\mathrm{<span\; class="notranslate">\; D.</span>}}\end{array}\right]<span\; class="notranslate">\; ,</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 2</span>}<span\; class="notranslate">\; )</span>$

in, is the upper left corner value of the 2x2 color gamut conversion unit 700, is the upper right corner value of the 2x2 color gamut conversion unit 700, is the lower left corner value of the 2x2 color gamut conversion unit 700, is the lower right corner value of the 2x2 color gamut conversion unit 700, the E element is the upper left corner value of the 2x2 frequency domain unit 750, the F element is the upper right corner value of the 2x2 frequency domain unit 750, and the G element is the 2x2 frequency domain unit 750 The value of the lower left corner of the H element is the lower right corner value of the 2x2 frequency domain unit 750, the 2x2 frequency domain unit 750 is divided into a brightness 2x2 frequency domain unit 760, a first chrominance 2x2 frequency domain unit 770 and a second chrominance 2x2 frequency domain unit 780 .

The value range of each element in the brightness 2x2 frequency domain unit 760 is -128 to 127, and the value range of each element in the first chroma 2x2 frequency domain unit 770 and the second chroma 2x2 frequency domain unit 780 is -255～255, so each element of the brightness 2x2 frequency domain unit 760 is 8 bits, each element of the first chroma 2x2 frequency domain unit 770 and the second chroma 2x2 frequency domain unit 780 is 9 bits, and this Computational only and does not affect the final encoded bit count.

The conversion matrix in formula (2) can be obtained by two-dimensional discrete cosine transformation, and formula (3) is a two-dimensional discrete cosine transformation formula:

$\mathrm{<span\; class="notranslate">\; f</span>}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; u</span>}<span\; class="notranslate">\; ,</span>\mathrm{<span\; class="notranslate">\; v</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; =</span>\frac{\mathrm{<span\; class="notranslate">\; 1</span>}}{\sqrt{\mathrm{<span\; class="notranslate">\; 2</span>}\mathrm{<span\; class="notranslate">\; N</span>}}}\mathrm{<span\; class="notranslate">\; c</span>}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; u</span>}<span\; class="notranslate">\; )</span>\mathrm{<span\; class="notranslate">\; c</span>}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; v</span>}<span\; class="notranslate">\; )</span>\underset{\mathrm{<span\; class="notranslate">\; x</span>}<span\; class="notranslate">\; =</span>\mathrm{<span\; class="notranslate">\; 0</span>}}{\overset{\mathrm{<span\; class="notranslate">\; N</span>}<span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; 1</span>}}{\mathrm{<span\; class="notranslate">\; \&Sigma;</span>}}}\underset{\mathrm{<span\; class="notranslate">\; the\; y</span>}<span\; class="notranslate">\; =</span>\mathrm{<span\; class="notranslate">\; 0</span>}}{\overset{\mathrm{<span\; class="notranslate">\; N</span>}<span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; 1</span>}}{\mathrm{<span\; class="notranslate">\; \&Sigma;</span>}}}\mathrm{<span\; class="notranslate">\; f</span>}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; x</span>}<span\; class="notranslate">\; ,</span>\mathrm{<span\; class="notranslate">\; the\; y</span>}<span\; class="notranslate">\; )</span>\mathrm{<span\; class="notranslate">\; cos</span>}<span\; class="notranslate">\; (</span>\frac{<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 2</span>}\mathrm{<span\; class="notranslate">\; x</span>}<span\; class="notranslate">\; +</span>\mathrm{<span\; class="notranslate">\; 1</span>}<span\; class="notranslate">\; )</span>\mathrm{<span\; class="notranslate">\; u\&pi;</span>}}{\mathrm{<span\; class="notranslate">\; 2</span>}\mathrm{<span\; class="notranslate">\; N</span>}}<span\; class="notranslate">\; )</span>\mathrm{<span\; class="notranslate">\; cos</span>}<span\; class="notranslate">\; (</span>\frac{<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 2</span>}\mathrm{<span\; class="notranslate">\; the\; y</span>}<span\; class="notranslate">\; +</span>\mathrm{<span\; class="notranslate">\; 1</span>}<span\; class="notranslate">\; )</span>\mathrm{<span\; class="notranslate">\; v\&pi;</span>}}{\mathrm{<span\; class="notranslate">\; 2</span>}\mathrm{<span\; class="notranslate">\; N</span>}}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; ,</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 3</span>}<span\; class="notranslate">\; )</span>$

in,

Among them, u, v are discrete frequency variables (discrete frequency variables), the values of u, v are 0, 1, 2, ..., N-1, f(x, y) is N×N image pixels, F( u, v) are the result of two-dimensional discrete cosine transformation, in this embodiment, N is 2, then the transformation matrix in formula (2) can be obtained.

In step S160, the 2x2 frequency domain unit 750 is classified into the first natural type 380 or the second natural type 390, wherein, when the F element and the G element of the first chroma 2x2 frequency domain unit 770 satisfy the following formula:

max(ABS(F,0),ABS(G,0))≤THD3,

And the F element and the G element of the second chroma 2x2 frequency domain unit 780 satisfy the following formula:

max(ABS(F,0),ABS(G,0))≤THD4,

Then determine that the 2x2 frequency domain unit 750 is the first natural type 380, otherwise, determine that the 2x2 frequency domain unit 750 is the second natural type 390, wherein THD3 is the third threshold value, and THD4 is the fourth threshold value (the first The values of the third threshold value and the fourth threshold value are selected by those skilled in the art based on experience), and the fourth threshold value THD4 is greater than the third threshold value THD3.

In step S170, the 2x2 frequency domain unit 750 is quantized and coded by looking up a table to generate second coded data.

In step S170, when the 2x2 frequency domain unit 750 is the first natural type 380, use 7 bits to record the E element, F element, and G element of the brightness 2x2 frequency domain unit 760; use 4 bits to record a 4-bit table position, the record content of the position of the 4-bit table is: among all the record contents of the 4-bit table, the value of the H element of the brightness 2×2 frequency domain unit 760 has the smallest difference.

The values of the elements of the brightness 2x2 frequency domain unit 760 are -128~127, so a shift operation needs to be performed first to shift the values of the elements of the brightness 2x2 frequency domain unit 760 from -128~127 to 0~ 255. In step S170, the numerical values of the E element, the F element, and the G element are quantized, and the decimal part is rounded off, and then recorded in 7 bits. Since the value of the E element, F element, and G element of the brightness 2x2 frequency domain unit 760 is 8 bits, when 7 bits are used for recording, the quantization factor Q is 2. The H element of the brightness 2x2 frequency domain unit 760 uses a 4-bit table for table lookup operation. The principle of the table lookup operation is the same as that of the aforementioned 7-bit table lookup table, and will not be repeated here.

In step S170, when the 2x2 frequency domain unit 750 is the first natural type 380, use 7 bits to record the E element of the first chroma 2x2 frequency domain unit 770; use 2 bits to record a 2-bit table position, the 2 The record content of the bit table position is: among all the record contents of the 2-bit table, the smallest difference between the average value of the F element and the G element of the first chroma 2x2 frequency domain unit 770; An H element of the chroma 2x2 frequency domain unit 770 .

The value of the elements of the first chroma 2x2 frequency domain unit 770 is -255 to 255, so a shift operation needs to be performed first to change the value of the elements of the first chroma 2x2 frequency domain unit 770 from -255 to 255 Shift to 0~510. Therefore, the element of the first chroma 2x2 frequency domain unit 770 is 9 bits. When using 7 bits to record the E element of the first chroma 2x2 frequency domain unit 770, a quantization operation must be performed first, wherein the quantization factor Q is 4 .

It is to take the average value of the F element and G element of the first chroma 2x2 frequency domain unit 770, and then use the average value to look up a 2-bit table. The principle of the table lookup operation is the same as the aforementioned 7-bit table lookup ,No longer.

In step S170, when the 2x2 frequency domain unit 750 is the first natural type 380, use 7 bits to record the value of the E element of the second chroma 2x2 frequency domain unit 780; use 2 bits to record a 2-bit table position, The record content of the 2-bit table position is: among all the record contents of the 2-bit table, the smallest difference between the average value of the F element and the G element in the second chroma 2x2 frequency domain unit 780; 3 bits record a 3-bit table position, and the record content of the 3-bit table position is: among all the recorded contents of the 3-bit table, the difference between the value of the H element of the second chroma 2x2 frequency domain unit 780 the smallest.

The values of the elements of the second chroma 2x2 frequency domain unit 780 are -255 to 255, so a shift operation needs to be performed first to change the values of the elements of the second chroma 2x2 frequency domain unit 780 from -255 to 255 Shift to 0~510. Therefore, the elements of the second chroma 2x2 frequency domain unit 780 are 9 bits. When using 7 bits to record the E element of the second chroma 2x2 frequency domain unit 780, a quantization operation must be performed first, wherein the quantization factor Q is 4 .

It first takes the average value of the F element and the G element of the second chroma 2x2 frequency domain unit 780, and then uses the average value to look up a 2-bit table. The principle of the 2-digit table look-up is the same as that of the aforementioned 7-digit table look-up, and will not be repeated here.

In step S170, when the 2x2 frequency domain unit 750 is the second natural type 390, use 6 bits to record the quantized value of the E element of the brightness 2x2 frequency domain unit 760, and use 5 bits to record the brightness 2x2 frequency domain unit 760 The quantized value of the F element of 5 bits is used to record the quantized value of the G element of the brightness 2x2 frequency domain unit 760; 3 bits are used to record a 3-bit table position, and the record content of the 3-bit table position is: Among all the recorded contents, the smallest difference from the value of the H element of the brightness 2×2 frequency domain unit 760 . The quantization factor Q and the table lookup operation are known by those skilled in the art according to the technology of the present invention, and will not be repeated here.

In step S170, when the 2x2 frequency domain unit 750 is the second natural type 390, use 5 bits to record the quantized value of the E element of the first chroma 2x2 frequency domain unit 770; use 3 bits to record a 3-bit table position , the record content of the position of the 3-bit table is: among all the record contents of the 3-bit table, the minimum value difference with the value of the F element of the first chroma 2x2 frequency domain unit 770; use 3 bits to record a 3-bit table position, the record content of the 3-bit table position is: among all the record contents of the 3-bit table, the smallest difference between the value of the G element of the first chroma 2x2 frequency domain unit 770; The H element of the first chroma 2x2 frequency domain unit 770 is recorded.

In step S170, when the 2x2 frequency domain unit 750 is the second natural type 390, use 5 bits to record the quantized value of the E element of the second chroma 2x2 frequency domain unit 780; use 4 bits to record a 4-bit table position , the record content of the 4-bit table position is: among all the record contents of the 4-bit table, the minimum value of the difference with the value of the F element of the second chroma 2x2 frequency domain unit 780; use 4 bits to record a 4-bit table position, the record content of the 4-bit table position is: among all the record contents of the 4-bit table, the minimum value of the difference with the value of the G element of the second chroma 2x2 frequency domain unit 780; use 3-bit records a 3-bit table position, and the record content of the 3-bit table position is: among all the recorded contents of the 3-bit table, the difference between the value of the H element of the second chroma 2x2 frequency domain unit 780 the smallest.

In step S180, the first coded data or the second coded data is received, and the first coded data or the second coded data is packaged to generate a coded packet with a fixed bit size.

As shown in FIG. 4, step S180 uses 1 bit (main packet header) to record whether the 2x2 encoding unit 220 is a man-made type or a natural type, and then uses 2 bits (first sub-packet header) to record the 2x2 encoding Whether the unit 220 is one of the first artificial type, the second artificial type, the third artificial type, or the fourth to seventh artificial types, and finally use 2 bits (the second sub-packet header) to record whether the 2x2 encoding unit 220 is One of the fourth through seventh man-made types. Therefore, when the 2x2 encoding unit 220 is one of the first artificial type, the second artificial type, and the third artificial type, the bit count after its encoding and packaging is 48 bits (=1+2+8+7+8 +7+8+7), when the 2x2 encoding unit 220 is one of the fourth to seventh artificial types, the bit count after its encoding and packaging is still 48 bits (=1+2+2+8+7 +8+6+8+6). When the 2x2 coding unit 220 is a natural type, then use 1 bit (the second subpacket header) to record whether the 2x2 coding unit 220 is one of the first natural type or the second natural type, when the 2x2 coding unit When 220 is the first natural type, the bit count after its encoding and packaging is still 48 bits (=1+1+3×7+4+7+2+7+2+3), when the 2x2 encoding unit 220 is For the second natural type, the bit count after encoding and packaging is still 48 bits (=1+1+6+5+5+3+5+3+3+5+4+4+3).

Fig. 8 shows the extension of the man-made types in Fig. 3, which extends to seventeen types on the basis of the above-mentioned seven man-made types. Among them, the first artificial type to the seventh artificial type are consistent with the above; the eighth and ninth artificial types indicate that the four pixels are a combination of a horizontal stripe in the horizontal direction and two single points; the tenth and eleventh artificial type, indicating that the four pixels are a combination of a vertical stripe in the vertical direction and two single points; the twelfth and thirteenth man-made types, indicating that the four pixels are in a diagonal stripe at a 45-degree angle and two Single-point combination; the fourteenth to seventeenth man-made types are single-channel types, see the subsequent formula for details.

Corresponding to the above seventeen artificial types, the judgment order in step 120 is adjusted: first judge whether the 2x2 coding unit is one of the fourteenth to seventeenth artificial types, and then judge whether it is the first artificial type to the first artificial type One of the three man-made types is judged whether it is one of the fourth man-made type to the seventh man-made type, and then judged whether it is one of the eighth man-made man-made type to the thirteenth man-made man-made type.

The eighth artificial type represents the approximate (L) of the upper left pixel and the upper right pixel; the ninth artificial type represents the approximate (L) of the lower left pixel and the lower right pixel; the tenth artificial type , indicating that the upper left pixel and the lower left pixel are approximate (L); the eleventh artificial type indicates that the upper right pixel and the lower right pixel are approximate (L); the twelfth artificial type indicates that the The pixels in the upper left corner and the pixels in the lower right corner are approximate (L); the thirteenth artificial type represents the pixels in the lower left corner and the upper right corner are approximate (L).

According to the seventeen newly expanded artificial types, in step 120, when the following formula is met, it is determined that the 2x2 coding unit is the fourteenth artificial type:

A _r =A _g , A _g =A _b

B _r =B _g , B _g =B _b

C _r =C _g , C _g =C _b

D _r = D _g , D _g = D _b

Wherein, A is the pixel in the upper left corner, B is the pixel in the upper right corner, C is the pixel in the lower left corner, D is the pixel in the lower right corner, _Ar , _Ag , A _b are the red value of pixel A, Green value and blue value, B _r , B _g , B _b are red value, green value and blue value of pixel B respectively, C _r , C _g , C _b are red value, green value and blue value of pixel C respectively Color values, D _r , D _g , and D _b are the red value, green value, and blue value of the pixel D, respectively.

In step 120, when the following formula is met, it is determined that the 2x2 coding unit is the fifteenth artificial type:

A _g =0, A _b =0

B _g =0, B _b =0

C _g =0, C _b =0

D _g =0, D _b =0

In step 120, when the following formula is satisfied, it is determined that the 2x2 coding unit is the sixteenth artificial type:

A _r =0, A _b =0

B _r =0, B _b =0

C _r =0, C _b =0

D _r =0, D _b =0

In step 120, when the following formula is met, it is determined that the 2x2 coding unit is the seventeenth artificial type:

A _g =0, A _r =0

B _g =0, B _r =0

C _g =0, C _r =0

D _g =0, D _r =0

In step 120, when the following formula is satisfied, it is determined that the 2x2 coding unit is the first artificial type:

ABS(A _y , B _y )＜THDY1, ABS(C _y ,D _y )＜THDY1

ABS(A _u , B _u )＜THDU1, ABS(C _u ,D _u )＜THDU1

ABS (A _v , B _v ) < THDV1, ABS (C _v , D _v ) < THDV1

ABS(A _y ,B _y )+ABS(A _v ,B _v )+ABS(A _u ,B _u )≤ABS(A _y ,C _y )+ABS(A _v ,C _v )+ABS(A _u , C _u )

ABS(A _y ,B _y )+ABS(A _v ,B _v )+ABS(A _u ,B _u )≤ABS(D _y ,B _y )+ABS(D _v ,B _v )+ABS(D _u , _Bu )

ABS(C _y , D _y )+ABS(C _v ,D _v )+ABS(C _u ,D _u )≤ABS(D _y ,B _y )+ABS(D _v ,B _v )+ABS(D _u , B _u )

ABS(C _y , D _y )+ABS(C _v ,D _v )+ABS(C _u ,D _u )≤ABS(A _y ,C _y )+ABS(A _v ,C _v )+ABS(A _u , C _u )

Among them, ABS is the absolute value function of the difference between the two elements in the brackets, THDY1 is the brightness threshold value 1, THDU1 is the first chroma threshold value 1, and THDV1 is the second chroma threshold value 1 (each threshold value Values are selected by those skilled in the art based on experience), A is the upper left pixel, B is the upper right pixel, C is the lower left pixel, D is the lower right pixel, A _y , A _u , A _v are the brightness, first chroma and second chroma values of pixel A respectively; By _y , _Bu , B _v are respectively the brightness, first chroma and second chroma values of pixel B; _Cy , C _u , C _v are brightness, first chroma and second chroma values of pixel C respectively, D _y , _Du , D _v are brightness, first chroma and second chroma values of pixel D respectively ;

Wherein, the brightness, the first chromaticity and the second chromaticity value are obtained by the color gamut conversion formula from RGB to YUV in the above step S140:

$\left[\begin{array}{c}\mathrm{<span\; class="notranslate">\; Y</span>}\\ \mathrm{<span\; class="notranslate">\; u</span>}\\ \mathrm{<span\; class="notranslate">\; V</span>}\end{array}\right]<span\; class="notranslate">\; =</span>\left[\begin{array}{ccc}\mathrm{<span\; class="notranslate">\; 0.25</span>}& \mathrm{<span\; class="notranslate">\; 0.5</span>}& \mathrm{<span\; class="notranslate">\; 0.25</span>}\\ <span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; 0.5</span>}& \mathrm{<span\; class="notranslate">\; 1.0</span>}& <span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; 0.5</span>}\\ <span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; 1.0</span>}& \mathrm{<span\; class="notranslate">\; 0</span>}& \mathrm{<span\; class="notranslate">\; 1.0</span>}\end{array}\right]\left[\begin{array}{c}\mathrm{<span\; class="notranslate">\; r</span>}\\ \mathrm{<span\; class="notranslate">\; g</span>}\\ \mathrm{<span\; class="notranslate">\; b</span>}\end{array}\right]<span\; class="notranslate">\; ,</span>$

Among them, r is the red value of a pixel, g is the green value of the pixel, b is the blue value of the pixel, Y is the brightness of the pixel, U and V are the first chromaticity and second chromaticity of the pixel respectively. chroma.

In step 120, when the following formula is met, it is determined that the 2x2 coding unit is the second artificial type:

ABS(A _y ,C _y )＜THDY1, ABS(B _y ,D _y )＜THDY1

ABS(A _u ,C _u )＜THDU1, ABS(B _u ,D _u )＜THDU1

ABS(A _v ,C _v )＜THDV1, ABS(B _v ,D _v )＜THDV1

ABS(A _y , C _y )+ABS(A _v ,C _v )+ABS(A _u ,C _u )≤ABS(A _y ,B _y )+ABS(A _v ,B _v )+ABS(A _u , B _u )

ABS(A _y ,C _y )+ABS(A _v ,C _v )+ABS(A _u ,C _u )≤ABS(C _y ,D _y )+ABS(C _v ,D _v )+ABS(C _u , D _u )

ABS(B _y , D _y )+ABS(B _v ,D _v )+ABS(B _u ,D _u )≤ABS(A _y ,B _y )+ABS(A _v ,B _v )+ABS(A _u , B _u )

ABS(B _y , D _y )+ABS(B _v ,D _v )+ABS(B _u ,D _u )≤ABS(D _y ,C _y )+ABS(D _v ,C _v )+ABS(D _u , C _u )

In step 120, when the following formula is met, it is determined that the 2x2 coding unit is the third artificial type:

ABS(C _y , B _y )＜THDY1, ABS(A _y ,D _y )＜THDY1

ABS(C _u , B _u )＜THDU1, ABS(A _u ,D _u )＜THDU1

ABS (C _v , B _v ) < THDV1, ABS (A _v , D _v ) < THDV1

ABS(C _y ,B _y )+ABS(C _v ,B _v )+ABS(C _u ,B _u )≤ABS(A _y ,B _y )+ABS(A _v ,B _v )+ABS(A _u , B _u )

ABS(C _y ,B _y )+ABS(C _v ,B _v )+ABS(C _u ,B _u )≤ABS(D _y ,C _y )+ABS(D _v ,C _v )+ABS(D _u , C _u )

ABS(A _y , D _y )+ABS(A _v ,D _v )+ABS(A _u ,D _u )≤ABS(A _y ,B _y )+ABS(A _v ,B _v )+ABS(A _u , B _u )

ABS(A _y , D _y )+ABS(A _v ,D _v )+ABS(A _u ,D _u )≤ABS(D _y ,C _y )+ABS(D _v ,C _v )+ABS(D _u , C _u )

In step 120, when the following formula is satisfied, it is determined that the 2x2 coding unit is the fourth artificial type:

ABS(D _y , B _y )＜THDY2, ABS(C _y ,D _y )＜THDY2

ABS(D _u , B _u )＜THDU2, ABS(C _u ,D _u )＜THDU2

ABS(D _v , B _v )＜THDV2, ABS(C _v ,D _v )＜THDV2

ABS(D _y ,B _y )+ABS(D _v ,B _v )+ABS(D _u ,B _u )≤ABS(A _y ,C _y )+ABS(A _v ,C _v )+ABS(A _u , C _u )

ABS(D _y ,B _y )+ABS(D _v ,B _v )+ABS(D _u ,B _u )≤ABS(A _y ,B _y )+ABS(A _v ,B _v )+ABS(A _u , B _u )

ABS(D _y , C _y )+ABS(D _v ,C _v )+ABS(D _u ,C _u )≤ABS(A _y ,C _y )+ABS(A _v ,C _v )+ABS(A _u , C _u )

ABS(D _y , C _y )+ABS(D _v ,C _v )+ABS(D _u ,C _u )≤ABS(A _y ,B _y )+ABS(A _v ,B _v )+ABS(A _u , B _u )

Among them, ABS is the absolute value function of the difference between the two elements in the brackets, THDY2 is the brightness threshold value 2, THDU2 is the first chromaticity threshold value 2, and THDV2 is the second chromaticity threshold value 2 (each threshold value The value is selected by those skilled in the art based on experience).

In step 120, when the following formula is satisfied, it is determined that the 2x2 coding unit is the fifth artificial type:

ABS(D _y , B _y )＜THDY2, ABS(A _y ,B _y )＜THDY2

ABS(D _u ，B _u )＜THDU2，ABS(A _u ，B _u )＜THDU2

ABS(D _v , B _v )＜THDV2, ABS(A _v ,B _v )＜THDV2

ABS(D _y ,B _y )+ABS(D _v ,B _v )+ABS(D _u ,B _u )≤ABS(A _y ,C _y )+ABS(A _v ,C _v )+ABS(A _u , C _u )

ABS(D _y ,B _y )+ABS(D _v ,B _v )+ABS(D _u ,B _u )≤ABS(C _y ,D _y )+ABS(C _v ,D _v )+ABS(C _u , D _u )

ABS(A _y ,B _y )+ABS(A _v ,B _v )+ABS(A _u ,B _u )≤ABS(A _y ,C _y )+ABS(A _v ,C _v )+ABS(A _u , C _u )

ABS(A _y ,B _y )+ABS(A _v ,B _v )+ABS(A _u ,B _u )≤ABS(C _y ,D _y )+ABS(C _v ,D _v )+ABS(C _u , D _u )

In step 120, when the following formula is met, it is determined that the 2x2 coding unit is the sixth artificial type:

ABS(A _y , B _y )＜THDY2, ABS(C _y ,A _y )＜THDY2

ABS(A _u ，B _u )＜THDU2，ABS(C _u ，A _u )＜THDU2

ABS(A _v , B _v )＜THDV2, ABS(C _v ,A _v )＜THDV2

ABS(A _y ,B _y )+ABS(A _v ,B _v )+ABS(A _u ,B _u )≤ABS(D _y ,C _y )+ABS(D _v ,C _v )+ABS(D _u , C _u )

ABS(A _y ,B _y )+ABS(A _v ,B _v )+ABS(A _u ,B _u )≤ABS(D _y ,B _y )+ABS(D _v ,B _v )+ABS(D _u , B _u )

ABS(A _y , C _y )+ABS(A _v ,C _v )+ABS(A _u ,C _u )≤ABS(D _y ,C _y )+ABS(D _v ,C _v )+ABS(D _u , C _u )

ABS(A _y , C _y )+ABS(A _v ,C _v )+ABS(A _u ,C _u )≤ABS(D _y ,B _y )+ABS(D _v ,B _v )+ABS(D _u , B _u )

In step 120, when the following formula is satisfied, it is determined that the 2x2 coding unit is the seventh artificial type:

ABS(A _y ,C _y )＜THDY2, ABS(C _y ,D _y )＜THDY2

ABS(A _u ,C _u )＜THDU2, ABS(C _u ,D _u )＜THDU2

ABS(A _v ,C _v )＜THDV2, ABS(C _v ,D _v )＜THDV2

ABS(A _y , C _y )+ABS(A _v ,C _v )+ABS(A _u ,C _u )≤ABS(B _y ,D _y )+ABS(B _v ,D _v )+ABS(B _u , D _u )

ABS(A _y , C _y )+ABS(A _v ,C _v )+ABS(A _u ,C _u )≤ABS(A _y ,B _y )+ABS(A _v ,B _v )+ABS(A _u , B _u )

ABS(D _y ,C _y )+ABS(D _v ,C _v )+ABS(D _u ,C _u )≤ABS(B _y ,D _y )+ABS(B _v ,D _v )+ABS(B _u , D _u )

ABS(D _y , C _y )+ABS(D _v ,C _v )+ABS(D _u ,C _u )≤ABS(A _y ,B _y )+ABS(A _v ,B _v )+ABS(A _u , B _u )

In step 120, when the following formula is satisfied, it is determined that the 2x2 coding unit is the eighth artificial type:

temp1=ABS(A _y , B _y )+ABS(A _v , B _v )+ABS(A _u , B _u )

temp2=ABS(A _y , C _y )+ABS(A _v ,C _y )+ABS(A _u ,C _u )

temp3=ABS(A _y , D _y )+ABS(A _v ,D _v )+ABS(A _u ,D _u )

temp4=ABS(D _y , B _y )+ABS(D _v , B _v )+ABS(D _u , B _u )

temp5=ABS(C _y , B _y )+ABS(C _v , B _v )+ABS(C _u , B _u )

temp6=ABS(C _y , D _y )+ABS(C _v , D _v )+ABS(C _u , D _u )

MIN(temp1, temp2, temp3, temp4, temp5, temp6) = temp1

ABS(A _y , B _y )＜THDY4

ABS( _Av , _Bv )＜THDV4

ABS(A _u ，B _u )＜THDU4

Or ABS(C _y , D _y )>THDY3

Or ABS(C _v , D _v )>THDV3

Or ABS(C _u , D _u )>THDU3

Among them, ABS is the absolute value function of the difference between the two elements in the brackets, THDY3 is the brightness threshold value 3, THDU3 is the first chromaticity threshold value 3, THDV3 is the second chromaticity threshold value 3, and THDY4 is the brightness threshold value Threshold 4, THDU4 is the first chroma threshold 4, THDV4 is the second chroma threshold 4 (values of each threshold are selected by those skilled in the art based on experience).

In step 120, when the following formula is satisfied, it is determined that the 2x2 coding unit is the ninth artificial type:

temp1=ABS(A _y , B _y )+ABS(A _v , B _v )+ABS(A _u , B _u )

temp2=ABS(A _y , C _y )+ABS(A _v , C _v )+ABS(A _u , C _u )

temp3=ABS(A _y , D _y )+ABS(A _v ,D _v )+ABS(A _u ,D _u )

temp4=ABS(D _y , B _y )+ABS(D _v , B _v )+ABS(D _u , B _u )

temp5=ABS(C _y , B _y )+ABS(C _v , B _v )+ABS(C _u , B _u )

temp6=ABS(C _y , D _y )+ABS(C _v , D _v )+ABS(C _u , D _u )

MIN(temp1, temp2, temp3, temp4, temp5, temp6) = temp6

ABS(C _y , D _y )＜THDY4

ABS(C _v , D _v )＜THDV4

ABS(C _u ，D _u )＜THDU4

Or ABS(A _y , B _y )>THDY3

Or ABS(A _v , B _v )>THDV3

Or ABS(A _u , B _u )＞THDU3

In step 120, when the following formula is met, it is determined that the 2x2 coding unit is the tenth artificial type:

temp1=ABS(A _y , B _y )+ABS(A _v , B _v )+ABS(A _u , B _u )

temp2=ABS(A _y , C _y )+ABS(A _v , C _v )+ABS(A _u , C _u )

temp3=ABS(A _y , D _y )+ABS(A _v ,D _v )+ABS(A _u ,D _u )

temp4=ABS(D _y , B _y )+ABS(D _v , B _v )+ABS(D _u , B _u )

temp5=ABS(C _y , B _y )+ABS(C _v , B _v )+ABS(C _u , B _u )

temp6=ABS(C _y , D _y )+ABS(C _v , D _v )+ABS(C _u , D _u )

MIN(temp1, temp2, temp3, temp4, temp5, temp6) = temp2

ABS(A _y , C _y )＜THDY4

ABS(A _v , C _v )＜THDV4

ABS(A _u ，C _u )＜THDU4

Or ABS(B _y , D _y )>THDY3

Or ABS(B _v , D _v )>THDV3

Or ABS(B _u , D _u )>THDU3

In step 120, when the following formula is satisfied, it is determined that the 2x2 coding unit is the eleventh artificial type:

temp1=ABS(A _y , B _y )+ABS(A _v , B _v )+ABS(A _u , B _u )

temp2=ABS(A _y , C _y )+ABS(A _v , C _v )+ABS(A _u , C _u )

temp3=ABS(A _y , D _y )+ABS(A _v ,D _v )+ABS(A _u ,D _u )

temp4=ABS(D _y , B _y )+ABS(D _v , B _v )+ABS(D _u , B _u )

temp5=ABS(C _y , B _y )+ABS(C _v , B _v )+ABS(C _u , B _u )

temp6=ABS(C _y , D _y )+ABS(C _v , D _v )+ABS(C _u , D _u )

MIN(temp1, temp2, temp3, temp4, temp5, temp6) = temp4

ABS(B _y ,B _y )＜THDY4

ABS(D _v ，B _v )＜THDV4

ABS(D _u ，B _u )＜THDU4

Or ABS(C _y , A _y )>THDY3

Or ABS(C _v , A _v )>THDV3

Or ABS(C _u , A _u )>THDU3

In step 120, when the following formula is satisfied, it is determined that the 2x2 coding unit is the twelfth artificial type:

temp1=ABS(A _y , B _y )+ABS(A _v , B _v )+ABS(A _u , B _u )

temp2=ABS(A _y , C _y )+ABS(A _v , C _v )+ABS(A _u , C _u )

temp3=ABS(A _y , D _y )+ABS(A _v ,D _v )+ABS(A _u ,D _u )

temp4=ABS(D _y , B _y )+ABS(D _v , B _v )+ABS(D _u , B _u )

temp5=ABS(C _y , B _y )+ABS(C _v , B _v )+ABS(C _u , B _u )

temp6=ABS(C _y , D _y )+ABS(C _v , D _v )+ABS(C _u , D _u )

MIN(temp1, temp2, temp3, temp4, temp5, temp6) = temp3

ABS(A _y , D _y )＜THDY4

ABS(A _v , D _v )＜THDV4

ABS(A _u ，D _u )＜THDU4

Or ABS(C _y , B _y )>THDY3

Or ABS(C _v , B _v )>THDV3

Or ABS(C _u , B _u )>THDU3

In step 120, when the following formula is satisfied, it is determined that the 2x2 coding unit is the thirteenth artificial type:

temp1=ABS(A _y , B _y )+ABS(A _v , B _v )+ABS(A _u , B _u )

temp2=ABS(A _y , C _y )+ABS(A _v , C _v )+ABS(A _u , C _u )

temp3=ABS(A _y , D _y )+ABS(A _v ,D _v )+ABS(A _u ,D _u )

temp4=ABS(D _y , B _y )+ABS(D _v , B _v )+ABS(D _u , B _u )

temp5=ABS(C _y , B _y )+ABS(C _v , B _v )+ABS(C _u , B _u )

temp6=ABS(C _y , D _y )+ABS(C _v , D _v )+ABS(C _u , D _u )

MIN(temp1, temp2, temp3, temp4, temp5, temp6) = temp5

ABS(C _y ,B _y )＜THDY4

ABS( _Cv , _Bv )＜THDV4

ABS(C _u ，B _u )＜THDU4

Or ABS(A _y , D _y )>THDY3

Or ABS(A _v , D _v )>THDV3

Or ABS(A _u ，D _u )＞THDU3

In step S160, in addition to the above natural type classification method, the natural type can also be divided as follows: the 2x2 frequency domain unit is divided into the first natural type, the second natural type or the third natural type, wherein:

When the H element of the first chroma 2x2 frequency domain unit satisfies the following formula,

H>THD1

Then determine that the 2x2 coding unit is the first natural type;

When the F element and the G element in the first chroma 2x2 frequency domain unit satisfy the following formula,

MAX(ABS(F,0),ABS(G,0))≤THD2

And the F element and the G element in the second chroma 2x2 frequency domain unit satisfy the following formula,

MAX(ABS(F,0),ABS(G,0))≤THD3

Then determine that the 2x2 coding unit is the second natural type;

If the conditions of the first natural type and the second natural type are not met, the 2x2 coding unit is determined to be the third natural type;

Wherein, THD1 is the first threshold value, THD2 is the second threshold value, and THD3 is the third threshold value (values of each threshold value are selected by those skilled in the art based on experience).

FIG. 9 is a schematic diagram of differential error coding, quantization and table look-up coding using the above-mentioned 17 artificial types of 2×2 coding units after extension. In FIG. 9 , numbers indicate the number of digits, for example, 8 and 7 respectively indicate 8 bits and 7 bits, slashes indicate table lookup operations, and backslashes indicate quantization operations.

In step S130, when the 2x2 encoding unit 220 is one of the first artificial type, the second artificial type and the third artificial type, use 8 bits to record the average value of two pixels, use 6 bits or 7 bits to record a 6-bit or 7-bit table position, the record content of the 6-bit or 7-bit table position is: among all the record content of the 6-bit or 7-bit table, the average value of the other two pixels in the 2x2 coding unit and the aforementioned use The difference between the average values of two pixels recorded by 8 bits is the smallest. For example, the 2x2 coding unit shown in Figure 10 only records: (128+128)/2=128 (using 8-bit recording) and the difference (127+127)/2-(128+128)/2=- 1 (recorded using a 7-digit table).

In step S130, when the 2x2 encoding unit 220 is one of the fourth artificial type to the seventh artificial type, use 8 bits to record the average value of three pixels, and use 7 bits or 6 bits to record the average value of the 2x2 encoding unit. The quantized value of another pixel. For example, referring to Figure 11, first add the color value of pixel B (127), the color value of pixel C (129) and the color value of pixel D (128), then divide by 3 to get 128, and then round up to get 128, using 8 bits Record the value 128. Quantize the color value (28) of pixel A, and then round off the decimal part to obtain the value 7, and use 6 bits to record the value 7. When the color of pixel A is green, the value 14 is recorded using 7 bits. The quantization operation is calculated by the aforementioned quantization formula, which will not be repeated here.

In step S130, when the 2x2 encoding unit 220 is one of the eighth artificial type to the thirteenth artificial type, use 5 bits to record the quantized value of the average value of two pixels, and use 4 bits to record the quantized values of the remaining two pixels respectively value; or use 7 bits to record the quantized value of the average value of two pixels, and use 5 bits to record the quantized value of the remaining two pixels. That is to take the average value of two similar pixel color values, perform quantization operation, and use 7 bits (or 5 bits) for recording, and the remaining two pixel color values are directly quantized and use 5 bits (or 4 bits) respectively Make a note. For example, with reference to Figure 12, first add the color value (21) of pixel B and the color value (23) of pixel D and then divide by 2 to obtain 22, perform quantization operation on 22 to obtain round(22/2)=11, use 7 Record the value 11 in bits; quantize the color value (7) of pixel A, and then round the decimal part to obtain the value 1, use 5 bits to record the value 1; perform quantization operation on the color value (40) of pixel C, and then round the decimal part To get the value 5, use 5 bits to record the value 5.

In step S130, when the 2x2 encoding unit 220 is one of the fourteenth artificial type to the seventeenth artificial type, it can be known from the above formulas about the fourteenth artificial type to the seventeenth artificial type that the so-called single channel is Pixels only have red (R), green (G), blue (B) or gray level (gray level) data, so this data is only 1/3 of the 24-bit three-channel data of RGB, so 8 bits can be used for this The data is fully recorded.

For the division methods of the above three natural types, please refer to Figure 13, where a backslash indicates a quantization operation, and a slash indicates a table lookup operation.

Among them, the quantization operation adopts the formula:

${\mathrm{<span\; class="notranslate">\; x</span>}}_{\mathrm{<span\; class="notranslate">\; Q</span>}}<span\; class="notranslate">\; =</span>\mathrm{<span\; class="notranslate">\; Round</span>}<span\; class="notranslate">\; (</span>\frac{\mathrm{<span\; class="notranslate">\; x</span>}}{\mathrm{<span\; class="notranslate">\; Q</span>}}<span\; class="notranslate">\; )</span>$

Where Q is a known quantization factor, Round is a rounding function, and the quantized value x _Q is recorded.

For example, if 7 bits are used to record 0 to 255, then Q=256/(2 ⁷ )=2.

Regarding the table look-up operation, for example, with reference to Fig. 14, there are 2 ⁴ = 16 record values in the 4-bit table, if the element value is the closest to the jth value in the table, then record "j", and the value of "j" can be as follows Formula calculation:

[a ₁ , a ₂ , a ₃ ,..., a _k-2 , a _k-1 , a _k ],

sign[ _Faj ]·sign[aj ₊₁ -F]≥0, (2)

Wherein, a ₁ to a _k are 16 values recorded in the 4-bit table, which are arranged in order from small to large. sign is a function that outputs the sign of the value, and F is the value to be looked up in the table. Once the formula (2) is satisfied, the j value is stored.

In step S170, quantization and table look-up encoding are performed on the 2x2 frequency domain unit to generate second encoded data.

In step S170, when the 2x2 frequency domain unit is the first natural type, use 5 bits to record the quantized values of the E element, F element, and G element of the brightness 2x2 frequency domain unit; use 3 bits to record a 3-bit table Position, the record content of the position of the 3-bit table is: among all the record content of the 3-bit table, the value of the H element of the brightness 2x2 frequency domain unit has the smallest difference.

The values of the elements of the brightness 2x2 frequency domain unit are -128~127, so a shift operation is required to shift the values of the elements of the brightness 2x2 frequency domain unit from -128~127 to 0~255. In step S170, quantize the values of the E element, F element, and G element, round off the decimal part, and then use 5 bits to record. Since the value of the E element, F element, and G element of the brightness 2x2 frequency domain unit is 8 bits, when 5 bits are used for recording, the quantization factor Q is 8. The H element of the luminance 2x2 frequency domain unit uses a 3-bit table for table lookup operation. The principle of the table lookup operation is the same as that of the aforementioned 5-bit table lookup table, and will not be repeated here.

In step S170, when the 2x2 frequency domain unit is the first natural type, use 5 bits to record the quantized value of the E element of the first chroma 2x2 frequency domain unit; use 3 bits to record a 3-bit table position, the 3 The record content of the bit table position is: among all the record contents of the 3-bit table, the one with the smallest value difference with the value of the F element of the first chroma 2x2 frequency domain unit; use 3 bits to record a 3-bit table position, the The record content of the 3-bit table position is: among all the record contents of the 3-bit table, the one with the smallest value difference with the value of the G element of the first chroma 2x2 frequency domain unit; use 3-bit record-3-bit table position, The record content of the position of the 3-bit table is: among all the record contents of the 3-bit table, the value of the H element of the first chroma 2×2 frequency domain unit 770 has the smallest difference.

In step S170, when the 2x2 frequency domain unit is the first natural type, use 5 bits to record the quantized value of the E element of the second chroma 2x2 frequency domain unit; use 3 bits to record a 3-bit table position, the 3 The record content of the bit table position is: among all the recorded contents of the 3-bit table, the one with the smallest value difference with the value of the F element of the second chroma 2x2 frequency domain unit; use 3 bits to record a 3-bit table position, the The record content of the 3-bit table position is: among all the record contents of the 3-bit table, the one with the smallest value difference with the value of the G element of the second chroma 2x2 frequency domain unit; use 3-bit record-3-bit table position, The record content of the position of the 3-bit table is: among all the record contents of the 3-bit table, the value of the H element of the second chroma 2×2 frequency domain unit has the smallest difference.

In step S170, when the 2x2 frequency domain unit is the second natural type, use 7 bits to record the quantized values of the E element, F element, and G element of the brightness 2x2 frequency domain unit; use 4 bits to record a 4-bit table Position, the record content of the position of the 4-bit table is: among all the record content of the 4-bit table, the value of the H element of the brightness 2x2 frequency domain unit has the smallest difference.

The values of the elements of the brightness 2x2 frequency domain unit are -128~127, so a shift operation is required to shift the values of the elements of the brightness 2x2 frequency domain unit from -128~127 to 0~255. In step S170, the numerical values of the E element, the F element, and the G element are quantized, and the decimal part is rounded off, and then recorded in 7 bits. Since the value of the E element, F element, and G element of the brightness 2x2 frequency domain unit is 8 bits, when 7 bits are used for recording, the quantization factor Q is 2. The H element of the luminance 2x2 frequency domain unit uses a 4-bit table for table lookup operation. The principle of the table lookup operation is the same as the aforementioned 7-bit table lookup table, and will not be repeated here.

In step S170, when the 2x2 frequency domain unit is the second natural type, use 6 bits to record the quantized value of the E element of the first chroma 2x2 frequency domain unit; use 2 bits to record a 2-bit table position, the 2 The record content of the bit table position is: among all the record contents of the 2-bit table, the smallest difference between the average value of the F element and the G element of the first chroma 2x2 frequency domain unit; the first chroma 2x2 frequency domain unit is not recorded H element of the chroma 2x2 frequency domain unit.

The values of the elements of the first chroma 2x2 frequency domain unit are -255 to 255, so a shift operation needs to be performed first to shift the values of the elements of the first chroma 2x2 frequency domain unit from -255 to 255 to 0~510. Therefore, the element of the first chroma 2x2 frequency domain unit 770 is 9 bits. When using 6 bits to record the E element of the first chroma 2x2 frequency domain unit 770, a quantization operation needs to be performed first, wherein the quantization factor Q is 8 .

It is to take the average value of the F element and the G element of the first chroma 2x2 frequency domain unit, and then use the average value to look up a 2-bit table. The principle of the table lookup operation is the same as the aforementioned 7-bit table lookup. No longer.

In step S170, when the 2x2 frequency domain unit is the second natural type, use 7 bits to record the quantized value of the E element of the second chroma 2x2 frequency domain unit; use 2 bits to record a 2-bit table position, the 2 The record content of the bit table position is: among all the record contents of the 2-bit table, the smallest difference between the average value of the F element and the G element in the second chroma 2x2 frequency domain unit; use 3-bit records A 3-bit table location, the record content of the 3-bit table location is: the smallest difference between all the record contents of the 3-bit table and the value of the H element of the second chroma 2x2 frequency domain unit.

The values of the elements of the second chroma 2x2 frequency domain unit are -255 to 255, so a shift operation needs to be performed first to shift the values of the elements of the second chroma 2x2 frequency domain unit from -255 to 255 to 0~510. Therefore, the element of the second chroma 2x2 frequency domain unit 780 is 9 bits. When using 7 bits to record the E element of the second chroma 2x2 frequency domain unit, a quantization operation needs to be performed first, wherein the quantization factor Q is 4.

It is to take the average value of the F element and the G element of the second chroma 2x2 frequency domain unit first, and then use the average value to look up a 2-bit table. The principle of the 2-digit table look-up is the same as that of the aforementioned 7-digit table look-up, and will not be repeated here.

In step S170, when the 2x2 frequency domain unit is the third natural type, use 5 bits to record the quantized value of the E element of the brightness 2x2 frequency domain unit; use 3 bits to record a 3-bit table position, the 3-bit table The record content of the position is: among all the record contents of the 3-bit table, the minimum value difference with the value of the F element of the brightness 2x2 frequency domain unit; use 3 bits to record a 3-bit table position, the 3-bit The record content of the table position is: among all the record contents of the 3-bit table, the minimum value difference with the value of the G element of the brightness 2x2 frequency domain unit; use 2 bits to record a 2-bit table position, the 2 The record content of the position of the bit table is: among all the record contents of the 2-bit table, the smallest difference between the value of the H element of the brightness 2x2 frequency domain unit.

In step S170, when the 2x2 frequency domain unit is the third natural type, use 4 bits to record the quantized value of the E element of the first chroma 2x2 frequency domain unit; use 4 bits to record a 4-bit table position, the 4 bits The record content of the bit table position is: among all the record contents of the 4-bit table, the minimum value difference with the value of the F element of the first chroma 2x2 frequency domain unit; use 4 bits to record a 4-bit table position , the record content of the 4-bit table position is: among all the record contents of the 4-bit table, the minimum value difference with the value of the G element of the first chroma 2×2 frequency domain unit; use 4 bits to record—4 Bit table position, the record content of the 4-bit table position is: the smallest difference between all the record contents of the 4-bit table and the value of the H element of the first chroma 2x2 frequency domain unit.

In step S170, when the 2x2 frequency domain unit is the third natural type, use 4 bits to record the quantized value of the E element of the second chroma 2x2 frequency domain unit; use 4 bits to record a 4-bit table position, the 4 bits The record content of the bit table position is: among all the record contents of the 4-bit table, the minimum value difference with the value of the F element of the second chroma 2x2 frequency domain unit; use 4 bits to record a 4-bit table position , the record content of the 4-bit table position is: among all the record contents of the 4-bit table, the minimum value difference with the value of the G element of the second chroma 2×2 frequency domain unit; use 4 bits to record—4 Bit table position, the record content of the 4-bit table position is: the smallest difference between all the record contents of the 4-bit table and the value of the H element of the second chroma 2x2 frequency domain unit.

In the hardware architecture, OTP (One Time Programmable, one-time programmable chip), ROM (Read-Only Memory, read-only memory) or NVM (Nonvolatile memory, non-volatile memory) can be used to record the table content.

In step S180, the first coded data or the second coded data is received, and the first coded data or the second coded data is packaged to generate a coded packet with a fixed bit size.

As shown in Figures 9 and 13, step S180 uses 1 bit (the main packet header) to record whether the 2x2 encoding unit 220 is a man-made type or a natural type, and then uses 4 bits (the first sub-packet header) to record Whether the 2x2 encoding unit 220 is one of the first artificial type to the seventeenth artificial type. Therefore, when the 2x2 encoding unit 220 is one of the first artificial type, the second artificial type, and the third artificial type, the bit count after its encoding and packaging is 48 bits (=1+4+8+7+8 +6+8+6), when the 2x2 encoding unit 220 is one of the fourth to seventh artificial types, the bit count after encoding and packaging is still 48 bits (=1+4+8+7+8 +6+8+6), when the 2x2 encoding unit 220 is one of the eighth to the thirteenth man-made types, the bit count after its encoding and packaging is 48 bits (=1+4+5+4+4 +7+5+5+5+4+4), when the 2x2 coding unit 220 is one of the fourteenth to seventeenth man-made types, the bit count after its coding and packaging is 39 bits (=1+ 4+2+8+8+8+8). When the 2x2 coding unit 220 is a natural type, then use 1 bit (the second subpacket header) to record whether the 2x2 coding unit 220 is the first natural type or the second or third natural type, when the 2x2 coding unit When 220 is the first natural type, the bit count after its encoding and packaging is still 48 bits (=1+1+5+5+5+3+5+3+3+3+5+3+3+3) , when the 2x2 coding unit 220 is the second natural type or the third natural type, then use 1 bit (secondary packet header) to record whether the 2x2 coding unit 220 is the second natural type or the third natural type, when the When the 2x2 encoding unit 220 is the second natural type, the bit count after encoding and packaging is still 48 bits (=1+1+1+7+7+7+4+6+2+7+2+3), When the 2x2 encoding unit 220 is the third natural type, the bit count after encoding and packing is still 48 bits (=1+1+1+5+3+3+2+4+4+4+4+4 +4+4+4).

Embodiment 2: the three colors of red (r), blue (g) and green (b) of each pixel in the 2x2 encoding unit are all recorded in 6 bits, so the 2x2 encoding unit 220 is 72 (=6×3× 4 bit.

In the second embodiment, the artificial types refer to the seventeen types in Fig. 8 . Among them, the first artificial type to the seventh artificial type and the fourteenth artificial type to the seventeenth artificial type are the same as the rules in the first embodiment, and the eighth artificial type to the thirteenth artificial type are adjusted as follows.

In step 120, when the following formula is satisfied, it is determined that the 2x2 coding unit is the eighth artificial type:

temp1=ABS(A _y , B _y )+ABS(A _v , B _v )+ABS(A _u , B _u )

temp2=ABS(A _y , C _y )+ABS(A _v , C _v )+ABS(A _u , C _u )

temp3=ABS(A _y , D _y )+ABS(A _v ,D _v )+ABS(A _u ,D _u )

temp4=ABS(D _y , B _y )+ABS(D _v , B _v )+ABS(D _u , B _u )

temp5=ABS(C _y , B _y )+ABS(C _v , B _v )+ABS(C _u , B _u )

temp6=ABS(C _y , D _y )+ABS(C _v , D _v )+ABS(C _u , D _u )

MIN(temp1, temp2, temp3, temp4, temp5, temp6) = temp1

ABS(A _y , B _y )＜THDY4

ABS( _Av , _Bv )＜THDV4

ABS(A _u ，B _u )＜THDU4

In step 120, when the following formula is satisfied, it is determined that the 2x2 coding unit is the ninth artificial type:

temp1=ABS(A _y , B _y )+ABS(A _v , B _v )+ABS(A _u , B _u )

temp2=ABS(A _y , C _y )+ABS(A _v , C _v )+ABS(A _u , C _u )

temp3=ABS(A _y , D _y )+ABS(A _v ,D _v )+ABS(A _u ,D _u )

temp4=ABS(D _y , B _y )+ABS(D _v , B _v )+ABS(D _u , B _u )

temp5=ABS(C _y , B _y )+ABS(C _v , B _v )+ABS(C _u , B _u )

temp6=ABS(C _y , D _y )+ABS(C _v , D _v )+ABS(C _u , D _u )

MIN(temp1, temp2, temp3, temp4, temp5, temp6) = temp6

ABS(C _y , D _y )＜THDY4

ABS(C _v , D _v )＜THDV4

ABS(C _u ，D _u )＜THDU4

In step 120, when the following formula is met, it is determined that the 2x2 coding unit is the tenth artificial type:

temp1=ABS(A _y , B _y )+ABS(A _v , B _v )+ABS(A _u , B _u )

temp2=ABS(A _y , C _y )+ABS(A _v , C _v )+ABS(A _u , C _u )

temp3=ABS(A _y , D _y )+ABS(A _v ,D _v )+ABS(A _u ,D _u )

temp4=ABS(D _y , B _y )+ABS(D _v , B _v )+ABS(D _u , B _u )

temp5=ABS(C _y , B _y )+ABS(C _v , B _v )+ABS(C _u , B _u )

temp6=ABS(C _y , D _y )+ABS(C _v , D _v )+ABS(C _u , D _u )

MIN(temp1, temp2, temp3, temp4, temp5, temp6) = temp2

ABS(A _y , C _y )＜THDY4

ABS(A _v , C _v )＜THDV4

ABS(A _u ，C _u )＜THDU4

In step 120, when the following formula is satisfied, it is determined that the 2x2 coding unit is the eleventh artificial type:

temp1=ABS(A _y , B _y )+ABS(A _v , B _v )+ABS(A _u , B _u )

temp2=ABS(A _y , C _y )+ABS(A _v , C _v )+ABS(A _u , C _u )

temp3=ABS(A _y , D _y )+ABS(A _v ,D _v )+ABS(A _u ,D _u )

temp4=ABS(D _y , B _y )+ABS(D _v , B _v )+ABS(D _u , B _u )

temp5=ABS(C _y , B _y )+ABS(C _v , B _v )+ABS(C _u , B _u )

temp6=ABS(C _y , D _y )+ABS(C _v , D _v )+ABS(C _u , D _u )

MIN(temp1, temp2, temp3, temp4, temp5, temp6) = temp4

ABS(D _y ,B _y )＜THDY4

ABS(D _v ，B _v )＜THDV4

ABS(D _u ，B _u )＜THDU4

In step 120, when the following formula is satisfied, it is determined that the 2x2 coding unit is the twelfth artificial type:

temp1=ABS(A _y , B _y )+ABS(A _v , B _v )+ABS(A _u , B _u )

temp2=ABS(A _y , C _y )+ABS(A _v , C _v )+ABS(A _u , C _u )

temp3=ABS(A _y , D _y )+ABS(A _v ,D _v )+ABS(A _u ,D _u )

temp4=ABS(D _y , B _y )+ABS(D _v , B _v )+ABS(D _u , B _u )

temp5=ABS(C _y , B _y )+ABS(C _v , B _v )+ABS(C _u , B _u )

temp6=ABS(C _y , D _y )+ABS(C _v , D _v )+ABS(C _u , D _u )

MIN(temp1, temp2, temp3, temp4, temp5, temp6) = temp3

ABS(A _y , D _y )＜THDY4

ABS(A _v , D _v )＜THDV4

ABS(A _u ，D _u )＜THDU4

In step 120, when the following formula is satisfied, it is determined that the 2x2 coding unit is the thirteenth artificial type:

temp1=ABS(A _y , B _y )+ABS(A _v , B _v )+ABS(A _u , B _u )

temp2=ABS(A _y , C _y )+ABS(A _v , C _v )+ABS(A _u , C _u )

temp3=ABS(A _y , D _y )+ABS(A _v ,D _v )+ABS(A _u ,D _u )

temp4=ABS(D _y , B _y )+ABS(D _v , B _v )+ABS(D _u , B _u )

temp5=ABS(C _y , B _y )+ABS(C _v , B _v )+ABS(C _u , B _u )

temp6=ABS(C _y , D _y )+ABS(C _v , D _v )+ABS(C _u , D _u )

MIN(temp1, temp2, temp3, temp4, temp5, temp6) = temp5

ABS(C _y ,B _y )＜THDY4

ABS( _Cv , _Bv )＜THDV4

ABS(C _u ，B _u )＜THDU4

For the natural type in Embodiment 2, the following division can also be performed: divide the 2×2 frequency domain unit into the first natural type or the second natural type.

When the F element and the G element in the first chroma 2x2 frequency domain unit satisfy the following formula,

MAX(ABS(F,0),ABS(G,0))≤THD1

And the F element and the G element in the second chroma 2x2 frequency domain unit satisfy the following formula,

MAX(ABS(F,0),ABS(G,0))≤THD2

Then it is determined that the 2x2 coding unit is of the first natural type, otherwise it is determined that the 2x2 coding unit is of the second natural type. Wherein, as mentioned above, EFGH is the value of YUV after discrete cosine transformation, and THD1 and THD2 are threshold values.

Fig. 15 is a schematic diagram of differential error coding, quantization and table look-up coding using the above-mentioned 17 artificial types of 2x2 coding units after the expansion in Embodiment 2.

In step S130, when the 2x2 coding unit 220 is one of the first man-made type, the second man-made type and the third man-made type, the pixel represented by a blank square and the double arrow symbol indicates that two pixels are averaged, and only the For an average value, the pixels indicated by the slash (pixels less than 6 bits, such as 4 bits, 5 bits), only record the difference with the rest of the pixels, use the aforementioned table lookup method, that is, use 5 bits to record one 5 bits Table position, the record content of the 5-bit table position is: among all the record contents of the 5-bit table, the average value of the other two pixels in the 2x2 coding unit and the average value of the aforementioned two pixels recorded using 6 bits The one with the smallest difference. For example, the 2x2 coding unit shown in Figure 16 only records: (63+63)/2=63 (using 6-bit recording) and the difference (62+62)/2-(63+63)/2=- 1 (recorded using a 5-digit form).

In step S130, when the 2x2 encoding unit 220 is one of the fourth artificial type to the seventh artificial type, average the three similar pixel color values, and use 6 bits for recording, and dissimilar The color value of the pixel is quantized (the backslash in the figure indicates the quantized operation). For example, referring to Figure 17, first add the color value of pixel B (23), the color value of pixel C (25) and the color value of pixel D (24), divide by 3 to get 24, and then round up to get 24, using 6 bits Record the value 24. Quantize the color value (7) of pixel A, and then round off the decimal part to obtain the value 2, and use 4 bits to record the value 2. When the color of pixel A is green, the value 4 is recorded using 5 bits. The quantization operation is calculated by the aforementioned quantization formula, which will not be repeated here.

In step S130, when the 2x2 encoding unit 220 is one of the eighth artificial type to the thirteenth artificial type, two similar pixel color values are averaged, and quantized, and use 5 bits (or 4 bits) for recording, and the other two pixel color values are directly quantized and recorded using 3 bits respectively. For example, with reference to Figure 18, the color value (21) of pixel B and the color value (23) of pixel D are added together and then divided by 2 to obtain 22, and the quantization operation is performed on 22 to obtain round(22/2)=11, use 5 1 bit (or 4 bits) to record the value 11; quantize the color value (7) of pixel A, and then round the decimal part to obtain the value 1, use 3 bits to record the value 1; quantize the color value (40) of pixel C , and then round the decimal part to obtain the value 5, and use 3 digits to record the value 5.

In step S130, when the 2x2 encoding unit 220 is one of the fourteenth artificial type to the seventeenth artificial type, it can be known from the above formulas about the fourteenth artificial type to the seventeenth artificial type that the so-called single channel is Pixels only have red (R), green (G), blue (B) or grayscale (grayle level) data, so this data is only 1/3 of the 24-bit three-channel data of RGB, so 6 bits can be used for this The data is fully recorded.

For the division methods of the above two natural types, please refer to Figure 19, where a backslash indicates a quantization operation, and a slash indicates a table lookup operation.

Among them, the quantization operation adopts the formula:

${\mathrm{<span\; class="notranslate">\; x</span>}}_{\mathrm{<span\; class="notranslate">\; Q</span>}}<span\; class="notranslate">\; =</span>\mathrm{<span\; class="notranslate">\; Round</span>}<span\; class="notranslate">\; (</span>\frac{\mathrm{<span\; class="notranslate">\; x</span>}}{\mathrm{<span\; class="notranslate">\; Q</span>}}<span\; class="notranslate">\; )</span>$

Where Q is a known quantization factor, Round is a rounding function, and the quantized value x _Q is recorded.

For example, if 5 bits are used to record 0 to 63, then Q=64/(2 ⁵ )=2.

Regarding the look-up table operation, for example, with reference to Fig. 20, there are 2 ³ =8 record values in the 3-bit table, if the element value is the closest to the jth value in the table, then record "j", and the value of "j" can be as follows Formula calculation:

[a ₁ , a ₂ , a ₃ ,..., a _k-2 , a _k-1 , a _k ],

sign[ _Faj ]·sign[aj ₊₁ -F]≥0, (2)

Wherein, a ₁ to a _k are 8 values recorded in the 3-digit table, which are arranged in order from small to large. sign is a function that outputs the sign of the value, and F is the value to be looked up in the table. Once the formula (2) is satisfied, the j value is stored.

When in step S120, it is determined that the 2x2 encoding unit 220 is not one of the first artificial type to the seventeenth artificial type, it means that the 2x2 encoding unit 220 is a natural type, so in step S140, the natural type The 2x2 encoding unit 220 performs color gamut conversion to obtain a 2x2 color gamut conversion unit.

In step S140, the values of the elements in the brightness 2x2 color gamut conversion unit 710 range from 0 to 63, and the elements of the first chroma 2x2 color gamut conversion unit 720 and the second chroma 2x2 color gamut conversion unit 730 The range of values is -63 to 63, so the elements of the brightness 2x2 color gamut conversion unit 710 are 6 bits, and the elements of the first chroma 2x2 color gamut conversion unit 720 and the second chroma 2x2 color gamut conversion unit 730 is 7 bits, and this is only a calculation process, which does not affect the final coded bit count. Before proceeding to the next step S150 , the values of the elements of the brightness 2×2 color gamut conversion unit 710 need to be shifted from 0˜63 to −32˜31.

In step S150, the value of each element in the brightness 2x2 frequency domain unit 760 ranges from -32 to 31, each element of the first chroma 2x2 frequency domain unit 770 and the second chroma 2x2 frequency domain unit 780 The range of values is -63 to 63, so each element of the brightness 2x2 frequency domain unit 760 is 6 bits, each element of the first chroma 2x2 frequency domain unit 770 and the second chroma 2x2 frequency domain unit 780 is 7 bits, and this is only a calculation process and does not affect the final encoded bit count.

In step S170, when the 2x2 frequency domain unit 750 is the first natural type 380, use 5 bits to record the E element, F element, and G element of the brightness 2x2 frequency domain unit 760; use 3 bits to record a 3-bit table position, the record content of the position of the 3-bit table is: among all the record contents of the 3-bit table, the value of the H element of the brightness 2×2 frequency domain unit 760 has the smallest difference.

The values of the elements of the brightness 2x2 frequency domain unit 760 are -32~31, so a shift operation needs to be performed first to shift the values of the elements of the brightness 2x2 frequency domain unit 760 from -32~31 to 0~ 63. In step S170, quantize the values of the E element, F element, and G element, round off the decimal part, and then use 5 bits to record. Since the value of the E element, F element, and G element of the brightness 2x2 frequency domain unit 760 is 6 bits, when 5 bits are used for recording, the quantization factor Q is 2. The H element of the brightness 2×2 frequency domain unit 760 uses a 3-bit table for table lookup operation. The principle of the table lookup operation is the same as that of the aforementioned 5-bit table lookup table, and will not be repeated here.

In step S170, when the 2x2 frequency domain unit 750 is the first natural type 380, use 5 bits to record the E element of the first chroma 2x2 frequency domain unit 770; use 2 bits to record a 2-bit table position, the 2 The record content of the bit table position is: among all the record contents of the 2-bit table, the smallest difference between the average value of the F element and the G element of the first chroma 2x2 frequency domain unit 770; An H element of the chroma 2x2 frequency domain unit 770 .

The value of the elements of the first chroma 2x2 frequency domain unit 770 is -63 to 63, so a shift operation needs to be performed first to change the value of the elements of the first chroma 2x2 frequency domain unit 770 from -63 to 63 Shift to 0~126. Therefore, the element of the first chroma 2x2 frequency domain unit 770 is 7 bits. When using 5 bits to record the E element of the first chroma 2x2 frequency domain unit 770, a quantization operation must be performed first, wherein the quantization factor Q is 4 .

It is to take the average value of the F element and G element of the first chroma 2x2 frequency domain unit 770, and then use the average value to look up a 2-bit table. The principle of the table lookup operation is the same as the aforementioned 5-bit table lookup. ,No longer.

In step S170, when the 2x2 frequency domain unit 750 is the first natural type 380, use 5 bits to record the quantized value of the E element of the second chroma 2x2 frequency domain unit 780; use 2 bits to record a 2-bit table position , the record content of the position of the 2-bit table is: among all the record contents of the 2-bit table, the smallest difference between the average value of the F element and the G element in the second chroma 2x2 frequency domain unit 780; Use 2 bits to record a 2-bit table position, the record content of the 2-bit table position is: among all the recorded contents of the 2-bit table, and the difference between the value of the H element of the second chroma 2x2 frequency domain unit 780 the smallest.

The values of the elements of the second chroma 2x2 frequency domain unit 780 are -63 to 63, so a shift operation needs to be performed first to change the values of the elements of the second chroma 2x2 frequency domain unit 780 from -63 to 63 Shift to 0~126. Therefore, the element of the second chroma 2x2 frequency domain unit 780 is 7 bits. When using 5 bits to record the E element of the second chroma 2x2 frequency domain unit 780, a quantization operation must be performed first, wherein the quantization factor Q is 4 .

It first takes the average value of the F element and the G element of the second chroma 2x2 frequency domain unit 780, and then uses the average value to look up a 2-bit table. The principle of the 2-digit table lookup is the same as that of the aforementioned 5-digit table lookup, and will not be repeated here.

In step S170, when the 2x2 frequency domain unit 750 is the second natural type 390, use 4 bits to record the quantized value of the E element of the brightness 2x2 frequency domain unit 760; use 3 bits to record a 3-bit table position, the 3 The record content of the bit table position is: among all the record contents of the 3-bit table, the minimum value of the difference with the value of the F element of the brightness 2x2 frequency domain unit 760; use 3-bit record-3-bit table position, The record content of the position of the 3-bit table is: among all the recorded contents of the 3-bit table, the minimum value difference with the value of the G element of the brightness 2x2 frequency domain unit 760; use 2 bits to record a 2-bit table position, the record content of the position of the 2-bit table is: among all the record contents of the 2-bit table, the smallest difference between the value of the H element of the brightness 2x2 frequency domain unit 760 . The quantization factor Q and the table lookup operation are known by those skilled in the art according to the technology of the present invention, and will not be repeated here.

In step S170, when the 2x2 frequency domain unit 750 is the second natural type 390, use 3 bits to record the quantized value of the E element of the first chroma 2x2 frequency domain unit 770; use 3 bits to record a 3-bit table position , the record content of the position of the 3-bit table is: among all the record contents of the 3-bit table, the minimum value difference with the value of the F element of the first chroma 2x2 frequency domain unit 770; use 3 bits to record a 3-bit table position, the record content of the 3-bit table position is: among all the record contents of the 3-bit table, the smallest difference with the value of the G element of the first chroma 2x2 frequency domain unit 770; use 2-bit records a 2-bit table position, and the record content of the 2-bit table position is: among all the recorded contents of the 2-bit table, the difference between the value of the H element of the first chroma 2x2 frequency domain unit 760 the smallest.

In step S170, when the 2x2 frequency domain unit 750 is the second natural type 390, use 3 bits to record the quantized value of the E element of the second chroma 2x2 frequency domain unit 780; use 3 bits to record a 3-bit table position , the record content of the position of the 3-bit table is: among all the record contents of the 3-bit table, the smallest difference between the value of the F element of the second chroma 2x2 frequency domain unit 780; use 3 bits to record a 3-bit table position, the record content of the 3-bit table position is: among all the record contents of the 3-bit table, the minimum value of the difference with the value of the G element of the second chroma 2x2 frequency domain unit 780; use 2 Record a 2-bit table position, the record content of the 2-bit table position is: among all the recorded contents of the 2-bit table, the minimum value of the difference with the value of the H element of the second chroma 2x2 frequency domain unit 780 By.

In the hardware architecture, OTP (One Time Programmable, one-time programmable chip), ROM (Read-Only Memory, read-only memory) or NVM (Nonvolatile memory, non-volatile memory) can be used to record the table content.

As shown in Figures 15 and 19, step S180 uses 1 bit (the main packet header) to record whether the 2x2 encoding unit 220 is a man-made type or a natural type, and then uses 4 bits (the first sub-packet header) to record Whether the 2x2 encoding unit 220 is one of the first artificial type to the seventeenth artificial type. Therefore, when the 2x2 encoding unit 220 is one of the first artificial type, the second artificial type, and the third artificial type, the bit count after its encoding and packaging is 36 bits (=1+4+6+4+6 +5+6+4), when the 2x2 encoding unit 220 is one of the fourth to seventh artificial types, the bit count after its encoding and packaging is still 36 bits (=1+4+6+4+6 +5+6+4), when the 2x2 encoding unit 220 is one of the eighth to the thirteenth man-made types, the bit count after its encoding and packaging is 36 bits (=1+4+4+3+3 +5+3+3+4+3+3), when the 2x2 coding unit 220 is one of the fourteenth to seventeenth man-made types, the bit count after its coding and packaging is 31 bits (=1+ 4+2+6+6+6+6). When the 2x2 encoding unit 220 is a natural type, then use 1 bit (the second subpacket header) to record whether the 2x2 encoding unit 220 is the first natural type or the second natural type, when the 2x2 encoding unit 220 is the second natural type When a natural type, the bit count after its encoding and packaging is still 36 bits (=1+1+5+5+5+3+5+2+2+5+2), when the 2x2 encoding unit 220 is the first In the case of two natural types, the bit count after encoding and packaging is still 36 bits (=1+1+4+3+3+2+3+3+3+2+3+3+3+2).

Fig. 21 is a flow chart of a fixed compression rate image decompression method based on 2x2 coding units according to the present invention, which decodes a fixed-bit-size coded packet to generate a 2x2 decoding unit in an image, the 2x2 The decoding unit includes four pixels arranged in a matrix, and the image has at least one 2×2 decoding unit.

First, in step S805, an encoded packet is received.

In step S810, judge whether this coded packet is artificial type according to the main packet header (1 bit) of this encoded packet, if so, then determine that this encoded packet is an artificial type encoded packet, otherwise, determine that this encoded packet is a natural type encoded packets.

In step S815, judge whether it is one of the first artificial type to the third artificial type according to the first sub-packet header (2 bit) of the encoded packet for the encoded packet determined to be an artificial type, wherein, the first artificial type One artificial type is two horizontal stripes with four pixels in the horizontal direction, the second artificial type is two vertical stripes with four pixels in the vertical direction, and the third artificial type is two oblique stripes with four pixels in the direction of 45 degrees. .

In step S820, for the coded packets that are judged to be man-made types and are not the first man-made type to the third man-made type, judge according to the sub-packet header (2 bit) and the second sub-packet header (2 bit) of the coded pack Whether it is one of the fourth to seventh artificial types. Among them, the fourth artificial type to the seventh artificial type is a combination of four pixels in a triangle and a single point; the fourth artificial type is a pixel in the lower left corner, a pixel in the upper right corner, and a pixel in the lower right corner; the fifth artificial type is a pixel in the upper left corner, The upper right pixel and the lower right pixel are approximated; the sixth artificial type is the upper left pixel, the lower left pixel and the upper right pixel are approximated; the seventh artificial type is the upper left pixel, the lower left pixel and the lower right pixel are approximated.

In step S825, inverse quantization, inverse look-up table decoding, and inverse differential error decoding are performed on the artificial type encoded packet to generate a first decoded data.

In step S830, for the encoded packet of the natural type, it is judged to be the first natural type or the second natural type according to the second subpacket header (1 bit) of the encoded packet.

In step S835, inverse quantization and inverse table lookup decoding are performed on the encoded packet of the natural type to generate a second decoded data;

In step S840, a discrete cosine transform is performed on the second decoded data to generate a third decoded data. In step S840, the transformation matrix coefficients of the discrete cosine transformation are:

$\left[\begin{array}{c}\stackrel{<span\; class="notranslate">\; \&OverBar;</span>}{\mathrm{<span\; class="notranslate">\; A</span>}}\\ \stackrel{<span\; class="notranslate">\; \&OverBar;</span>}{\mathrm{<span\; class="notranslate">\; B</span>}}\\ \stackrel{<span\; class="notranslate">\; \&OverBar;</span>}{\mathrm{<span\; class="notranslate">\; C</span>}}\\ \stackrel{<span\; class="notranslate">\; \&OverBar;</span>}{\mathrm{<span\; class="notranslate">\; D.</span>}}\end{array}\right]\left[\begin{array}{cccc}\mathrm{<span\; class="notranslate">\; 1</span>}& \mathrm{<span\; class="notranslate">\; 1</span>}& \mathrm{<span\; class="notranslate">\; 1</span>}& \mathrm{<span\; class="notranslate">\; 1</span>}\\ \mathrm{<span\; class="notranslate">\; 1</span>}& <span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; 1</span>}& \mathrm{<span\; class="notranslate">\; 1</span>}& <span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; 1</span>}\\ \mathrm{<span\; class="notranslate">\; 1</span>}& \mathrm{<span\; class="notranslate">\; 1</span>}& <span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; 1</span>}& <span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; 1</span>}\\ \mathrm{<span\; class="notranslate">\; 1</span>}& <span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; 1</span>}& <span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; 1</span>}& \mathrm{<span\; class="notranslate">\; 1</span>}\end{array}\right]\left[\begin{array}{c}\mathrm{<span\; class="notranslate">\; E.</span>}\\ \mathrm{<span\; class="notranslate">\; f</span>}\\ \mathrm{<span\; class="notranslate">\; G</span>}\\ \mathrm{<span\; class="notranslate">\; h</span>}\end{array}\right]<span\; class="notranslate">\; .</span>$

Wherein, E, F, G, H are the second decoded data, for the third decoded data.

In step S845, color gamut conversion is performed on the third decoded data to obtain a fourth decoded data. In step S845, YUV to RGB color gamut conversion is carried out, and the conversion matrix coefficient of this YUV to RGB color gamut conversion is:

$\left[\begin{array}{c}\mathrm{<span\; class="notranslate">\; r</span>}\\ \mathrm{<span\; class="notranslate">\; g</span>}\\ \mathrm{<span\; class="notranslate">\; b</span>}\end{array}\right]<span\; class="notranslate">\; =</span>\left[\begin{array}{ccc}\mathrm{<span\; class="notranslate">\; 1.0</span>}& <span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; 0.5</span>}& <span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; 0.5</span>}\\ \mathrm{<span\; class="notranslate">\; 1.0</span>}& \mathrm{<span\; class="notranslate">\; 0.5</span>}& \mathrm{<span\; class="notranslate">\; 0</span>}\\ \mathrm{<span\; class="notranslate">\; 1.0</span>}& <span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; 0.5</span>}& \mathrm{<span\; class="notranslate">\; 0.5</span>}\end{array}\right]\left[\begin{array}{c}\mathrm{<span\; class="notranslate">\; Y</span>}\\ \mathrm{<span\; class="notranslate">\; u</span>}\\ \mathrm{<span\; class="notranslate">\; V</span>}\end{array}\right]<span\; class="notranslate">\; ,</span>$

Wherein, Y is the brightness of the pixel in the third decoded data, U and V are the chroma of the pixel, r is the red value of the pixel in the fourth decoded data, g is the green value of the pixel, and b is The blue value of this pixel.

In step S850, the first decoded data or the fourth decoded data is received, and the first decoded data or the fourth decoded data is reconstructed to generate a 2x2 decoding unit.

FIG. 22 is a structural diagram of a display system applying a fixed compression rate based on 2x2 coding units according to the present invention, which is used to compress and decompress display images. The display system 900 includes a display module 910 and an image input device 920 , a fixed compression rate image compression device 930 based on 2x2 coding units, a temporary storage device 940, a fixed compression rate image decompression device 950 based on 2x2 coding units, a timing controller 960, multiple source drivers 970 and multiple A gate driver 980.

The display module 910 is used for displaying images. The image input device 920 is used for inputting and displaying images. The fixed compression rate image compression device 930 based on a 2x2 coding unit is connected to the image input device 920, and is used for encoding a 2x2 coding unit of a display image to generate a coded packet corresponding to the 2x2 coding unit, wherein the image has at least A 2x2 code unit.

The temporary storage device 940 is connected to the 2x2 CU-based fixed compression rate image compression device 930 to temporarily store the encoded packets output by the 2x2 CU-based fixed compression rate image compression device 930 .

The fixed compression ratio image decompression device 950 based on 2x2 coding units is connected to the temporary storage device 940 to receive the encoded packets and decompress the encoded packets to generate 2x2 decoding units corresponding to the 2x2 coding units.

The timing controller 960 is connected to the fixed compression ratio image decompression device 950 based on 2x2 coding units, and is used for receiving 2x2 decoding units to generate timing driving signals and display data of the display module 910 .

A plurality of source drivers 970 and a plurality of gate drivers 980 are connected to the timing controller 960 for receiving timing driving signals and display data output by the timing controller 960 , and then driving the display module 910 .

The fixed compression rate image compression device 930 first determines whether the 2x2 coding unit is artificial or natural, and performs differential error coding, quantization, and table look-up coding on the artificial 2x2 coding unit to generate the first coded data, and the natural type The 2x2 coding unit performs color gamut conversion, discrete cosine transformation, quantization and table look-up coding, and then generates the second coded data, and then encapsulates the first coded data or the second coded data to generate a coded packet with a fixed compression rate . Wherein, the 2x2 encoding unit is 96 (24bit version) bits or 72 (18bit version) bits, and the encoding packet corresponding to the 2x2 encoding unit is 48 (24bit version) bits or 36 bits (18bit version).

It can be known from the foregoing description that the present invention uses a pixel size of 2x2 as a coding unit, and achieves image compression and Maintain image quality.

When the above encoding units are classified, the classification of artificial types helps to deal with specific patterns such as font edges, gray scale changes, jagged, checkerboard patterns, etc., and with the packet recording method of the present invention, lossless compression can be achieved for specific artificial types of encoding units.

In the natural type, the UV component of the YUV after the color gamut conversion in step S140 is less sensitive to human eyes, so the corresponding frequency domain elements are discarded or recorded with less bit count during packet recording. At the same time, the elements after discrete cosine transformation are in the frequency domain, and the high-frequency elements are less sensitive to the response of the human eye, and the high-frequency elements are recorded with fewer bit counts to retain information that is more sensitive to the response of the human eye.

Simultaneously, step S140, step S150, step S840, step S850 color gamut conversion or discrete cosine conversion, the coefficient of its conversion matrix is ±1,0.25,±0.5 when hardware realizes, can use shifter (shifter ) to replace the multiplier to save hardware cost.

In addition, when the technology of the present invention is applied to mobile phones, test patterns such as general artificial gray scales and checkerboard patterns of mobile phones can achieve lossless compression and decompression effects, and at the same time can save memory requirements for storing images on mobile phones. And each 2x2 coding unit operates independently when compressing or decompressing, without referring to other 2x2 coding units, and the compression rate of each coding unit is fixed at 0.5 (=36/72) or 0.5 (=48/96), no need Real-time compression and decompression can be performed by referring to any previous packet, pixel, frame, etc., that is, a single encoding unit can be entered to complete a single encoding package. Similarly, once a single encoded packet enters, it can be decompressed and restored to a single decoding unit, which is especially suitable for special applications of random access, such as partial update of mobile phone display memory.

From the above, it can be known that the present invention is different from the prior art in terms of purpose, means and effect, and has great practical value. It should be noted that the above-mentioned embodiments are only examples for the convenience of description, and the scope of rights claimed in the present invention should be based on the scope of the claims, rather than limited to the above-mentioned embodiments.

The above descriptions are only preferred embodiments of the present invention, and are not intended to limit the present invention. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principles of the present invention shall be included in the present invention. within the scope of protection.

Claims (76)

1. the image compressing method with fixing compression ratio based on 2x2 coding unit, is characterized in that: the 2x2 coding unit in image is encoded, and described image is made up of at least one 2x2 coding unit, and described image compressing method comprises the following steps:

(A) receive 2x2 coding unit, described 2x2 coding unit comprises the top left corner pixel, upper right corner pixel, lower left corner pixel and the lower right corner pixel that are matrix arrangement, and the each pixel in described 2x2 coding unit has red value, green numerical value and blue values;

(B) judge whether described 2x2 coding unit is artificial type, if, judge that this 2x2 coding unit is as this artificial type, otherwise, judge that this 2x2 coding unit is natural type, wherein, described artificial type comprises: the first artificial type, represents these four pixels two horizontal stripes in horizontal direction; The second artificial type, represents that these four pixels are two vertical stripes of vertical direction; The 3rd artificial type, represents that these four pixels are two slanted bar lines intersections of miter angle direction; The artificial type of the 4th artificial type to the seven, represents the combination with single-point triangular in shape of these four pixels;

(C) to being judged to be the 2x2 coding unit of the artificial type coding that carries out differential errors coding, quantizes and table look-up, to produce first coding data;

(D) the 2x2 coding unit that is judged to be natural type is carried out to RGB to YUV color gamut conversion, to obtain 2x2 gamut conversion unit;

(E) described 2x2 gamut conversion unit is carried out to discrete cosine transform, to produce 2x2 frequency domain unit; And

(F) described 2x2 frequency domain unit is quantized and the coding of tabling look-up, to produce the second coded data;

Described the first artificial type, represents that described top left corner pixel and upper right corner pixel are approximate, and described lower left corner pixel and lower right corner pixel approximate; Described the second artificial type represents that described top left corner pixel and lower left corner pixel are approximate, and described upper right corner pixel and lower right corner pixel approximate; Described the 3rd artificial type, represents that described top left corner pixel and lower right corner pixel are approximate, and described lower left corner pixel and upper right corner pixel approximate; Described the 4th artificial type, represents that described lower left corner pixel, upper right corner pixel and lower right corner pixel are approximate; Described the 5th artificial type, represents that described top left corner pixel, upper right corner pixel and lower right corner pixel are approximate; Described Sixth Man is made type, represents that described top left corner pixel, lower left corner pixel and upper right corner pixel are approximate; Described the 7th artificial type, represents that described top left corner pixel, lower left corner pixel and lower right corner pixel are approximate;

(G) receive described first coding data or the second coded data, and this first coding data or this second coded data are encapsulated, to produce the coding package with fixing compression ratio.

2. image compressing method as claimed in claim 1, it is characterized in that, described artificial type also comprises the 8th artificial type in artificial type～17, wherein: eight, the 9th artificial type, represents these four pixels horizontal stripe in horizontal direction and the combination of two single-points; Ten, the 11 artificial type, represents that these four pixels are the combination of a vertical stripe and two single-points of vertical direction; The the 12, the 13 artificial type, represents that these four pixels are a slanted bar line of miter angle direction and the combination of two single-points;

Described the 8th artificial type, represents that described top left corner pixel and upper right corner pixel are approximate; Described the 9th artificial type, represents that described lower left corner pixel and lower right corner pixel are approximate; Described the tenth artificial type, represents that described top left corner pixel and lower left corner pixel are approximate; Described the 11 artificial type, represents that described upper right corner pixel and lower right corner pixel are approximate; Described the 12 artificial type, represents that described top left corner pixel and lower right corner pixel are approximate; Described the 13 artificial type, represents that described lower left corner pixel and upper right corner pixel are approximate;

In described step (B), in the time meeting following formula, judge that described 2x2 coding unit is as the 14 artificial type:

A _r＝A _g,A _g＝A _b

B _r＝B _g,B _g＝B _b

C _r＝C _g,C _g＝C _b

D _r＝D _g,D _g＝D _b

In described step (B), in the time meeting following formula, judge that described 2x2 coding unit is as the 15 artificial type:

A _g＝0,A _b＝0

B _g＝0,B _b＝0

C _g＝0,C _b＝0

D _g＝0,D _b＝0

In described step (B), in the time meeting following formula, judge that described 2x2 coding unit is as the 16 artificial type:

A _r＝0,A _b＝0

B _r＝0,B _b＝0

C _r＝0,C _b＝0

D _r＝0,D _b＝0

In described step (B), in the time meeting following formula, judge that described 2x2 coding unit is as the 17 artificial type:

A _g＝0,A _r＝0

B _g＝0,B _r＝0

C _g＝0,C _r＝0

D _g＝0,D _r＝0

Wherein, A is described top left corner pixel, and B is described upper right corner pixel, and C is described lower left corner pixel, and D is described lower right corner pixel, A _r, A _gbe respectively the red value of pixel A, green numerical value and blue values, B _r, B _gbe respectively the red value of pixel B, green numerical value and blue values, C _r, C _gbe respectively the red value of pixel C, green numerical value and blue values, D _r, D _gbe respectively the red value of pixel D, green numerical value and blue values.

3. image compressing method as claimed in claim 1, it is characterized in that: in described step (B), first judge whether described 2x2 coding unit is in the artificial type of the first artificial type to the three, then judge whether described 2x2 coding unit is in the artificial type of the 4th artificial type to the seven.

4. image compressing method as claimed in claim 2, it is characterized in that, in described step (B), first judge whether described 2x2 coding unit is in the 14 to the 17 artificial type, determine whether again in the artificial type of the first artificial type to the three, determine whether again in the artificial type of the 4th artificial type to the seven, then determine whether in the artificial type of the 8th artificial type to the 13.

5. image compressing method as claimed in claim 3, is characterized in that: in described 2x2 coding unit, every kind of color numerical value adopts 8 bit representations.

6. image compressing method as claimed in claim 5, is characterized in that: in described step (B), in the time meeting following formula, judge that described 2x2 coding unit is as the first artificial type:

ABS(A _r,B _r)＜THD1,ABS(C _r,D _r)＜THD1,

ABS(A _g,B _g)＜THD1,ABS(C _g,D _g)＜THD1,

ABS(A _b,B _b)＜THD1,ABS(C _b,D _b)＜THD1,

ABS(A _r,B _r)+ABS(A _g,B _g)+ABS(A _b,B _b)≤

ABS(A _r,C _r)+ABS(A _g,C _g)+ABS(A _b,C _b),

ABS(A _r,B _r)+ABS(A _g,B _g)+ABS(A _b,B _b)≤

ABS(D _r,B _r)+ABS(D _g,B _g)+ABS(D _b,B _b),

ABS(C _r,D _r)+ABS(C _g,D _g)+ABS(C _b,D _b)≤

ABS(D _r,B _r)+ABS(D _g,B _g)+ABS(D _b,B _b),

ABS(C _r,D _r)+ABS(C _g,D _g)+ABS(C _b,D _b)≤

ABS(A _r,C _r)+ABS(A _g,C _g)+ABS(A _b,C _b),

Wherein, THD1 is the first threshold value, and A is described top left corner pixel, and B is described upper right corner pixel, and C is described lower left corner pixel, and D is described lower right corner pixel, A _r, A _g, A _bbe respectively the red value of pixel A, green numerical value and blue values, B _r, B _g, B _bbe respectively the red value of pixel B, green numerical value and blue values, C _r, C _g, C _bbe respectively the red value of pixel C, green numerical value and blue values, D _r, D _g, D _bbe respectively the red value of pixel D, green numerical value and blue values, ABS is the poor absolute value of bracket moderate-element.

7. image compressing method as claimed in claim 5, is characterized in that: in described step (B), in the time meeting following formula, judge that described 2x2 coding unit is as the second artificial type:

ABS(A _r,C _r)＜THD1,ABS(B _r,D _r)＜THD1,

ABS(A _g,C _g)＜THD1,ABS(B _g,D _g)＜THD1,

ABS(A _b,C _b)＜THD1,ABS(B _b,D _b)＜THD1,

ABS(A _r,C _r)+ABS(A _g,C _g)+ABS(A _b,C _b)≤

ABS(A _r,B _r)+ABS(A _g,B _g)+ABS(A _b,B _b),

ABS(A _r,C _r)+ABS(A _g,C _g)+ABS(A _b,C _b)≤

ABS(D _r,C _r)+ABS(D _g,C _g)+ABS(D _b,C _b),

ABS(B _r,D _r)+ABS(B _g,D _g)+ABS(B _b,D _b)≤

ABS(D _r,C _r)+ABS(D _g,C _g)+ABS(D _b,C _b),

ABS(B _r,D _r)+ABS(B _g,D _g)+ABS(B _b,D _b)≤

ABS(A _r,B _r)+ABS(A _g,B _g)+ABS(A _b,B _b),

Wherein, THD1 is the first threshold value, and A is described top left corner pixel, and B is described upper right corner pixel, and C is described lower left corner pixel, and D is described lower right corner pixel, A _r, A _g, A _bbe respectively the red value of pixel A, green numerical value and blue values, B _r, B _g, B _bbe respectively the red value of pixel B, green numerical value and blue values, C _r, C _g, C _bbe respectively the red value of pixel C, green numerical value and blue values, D _r, D _g, D _bbe respectively the red value of pixel D, green numerical value and blue values, ABS is the poor absolute value of bracket moderate-element.

8. image compressing method as claimed in claim 5, is characterized in that: in described step (B), in the time meeting following formula, judge that described 2x2 coding unit is as the 3rd artificial type:

ABS(A _r,D _r)＜THD1,ABS(C _r,B _r)＜THD1,

ABS(A _g,D _g)＜THD1,ABS(C _g,B _g)＜THD1,

ABS(A _b,D _b)＜THD1,ABS(C _b,B _b)＜THD1,

ABS(A _r,D _r)+ABS(A _g,D _g)+ABS(A _b,D _b)≤

ABS(A _r,B _r)+ABS(A _g,B _g)+ABS(A _b,B _b),

ABS(A _r,D _r)+ABS(A _g,D _g)+ABS(A _b,D _b)≤

ABS(D _r,C _r)+ABS(D _g,C _g)+ABS(D _b,C _b),

ABS(C _r,B _r)+ABS(C _g,B _g)+ABS(C _b,B _b)≤

ABS(D _r,C _r)+ABS(D _g,C _g)+ABS(D _b,C _b),

ABS(C _r,B _r)+ABS(C _g,B _g)+ABS(C _b,B _b)≤

ABS(A _r,B _r)+ABS(A _g,B _g)+ABS(A _b,B _b),

Wherein, THD1 is the first threshold value, and A is described top left corner pixel, and B is described upper right corner pixel, and C is described lower left corner pixel, and D is described lower right corner pixel, Ar, A _g, A _bbe respectively the red value of pixel A, green numerical value and blue values, B _r, B _g, B _bbe respectively the red value of pixel B, green numerical value and blue values, C _r, C _g, C _bbe respectively the red value of pixel C, green numerical value and blue values, D _r, D _g, D _bbe respectively the red value of pixel D, green numerical value and blue values, ABS is the poor absolute value of bracket moderate-element.

9. image compressing method as claimed in claim 5, is characterized in that: in described step (B), in the time meeting following formula, judge that described 2x2 coding unit is as the 4th artificial type:

ABS(B _r,D _r)＜THD2,ABS(C _r,D _r)＜THD2,

ABS(B _g,D _g)＜THD2,ABS(C _g,D _g)＜THD2,

ABS(B _b,D _b)＜THD2,ABS(C _b,D _b)＜THD2,

ABS(B _r,D _r)+ABS(B _g,D _g)+ABS(B _b,D _b)≤

ABS(A _r,C _r)+ABS(A _g,C _g)+ABS(A _b,C _b),

ABS(B _r,D _r)+ABS(B _g,D _g)+ABS(B _b,D _b)≤

ABS(A _r,B _r)+ABS(A _g,B _g)+ABS(A _b,B _b),

ABS(C _r,D _r)+ABS(C _g,D _g)+ABS(C _b,D _b)≤

ABS(A _r,B _r)+ABS(A _g,B _g)+ABS(A _b,B _b),

ABS(C _r,D _r)+ABS(C _g,D _g)+ABS(C _b,D _b)≤

ABS(A _r,C _r)+ABS(A _g,C _g)+ABS(A _b,C _b),

Wherein, THD2 is the second threshold value, and A is described top left corner pixel, and B is described upper right corner pixel, and C is described lower left corner pixel, and D is described lower right corner pixel, A _r, A _g, A _bbe respectively the red value of pixel A, green numerical value and blue values, B _r, B _g, B _bbe respectively the red value of pixel B, green numerical value and blue values, C _r, C _g, C _bbe respectively the red value of pixel C, green numerical value and blue values, D _r, D _g, D _bbe respectively the red value of pixel D, green numerical value and blue values, ABS is the poor absolute value of bracket moderate-element.

10. image compressing method as claimed in claim 5, is characterized in that: in described step (B), in the time meeting following formula, judge that described 2x2 coding unit is as the 5th artificial type:

ABS(B _r,D _r)＜THD2,ABS(A _r,B _r)＜THD2,

ABS(B _g,D _g)＜THD2,ABS(A _g,B _g)＜THD2,

ABS(B _b,D _b)＜THD2,ABS(A _b,B _b)＜THD2,

ABS(B _r,D _r)+ABS(B _g,D _g)+ABS(B _b,D _b)≤

ABS(A _r,C _r)+ABS(A _g,C _g)+ABS(A _b,C _b),

ABS(B _r,D _r)+ABS(B _g,D _g)+ABS(B _b,D _b)≤

ABS(C _r,D _r)+ABS(C _g,D _g)+ABS(C _b,D _b),

ABS(A _r,B _r)+ABS(A _g,B _g)+ABS(A _b,B _b)≤

ABS(C _r,D _r)+ABS(C _g,D _g)+ABS(C _b,D _b),

ABS(A _r,B _r)+ABS(A _g,B _g)+ABS(A _b,B _b)≤

ABS(A _r,C _r)+ABS(A _g,C _g)+ABS(A _b,C _b),

Wherein, THD2 is the second threshold value, and A is described top left corner pixel, and B is described upper right corner pixel, and C is described lower left corner pixel, and D is described lower right corner pixel, A _r, A _g, A _bbe respectively the red value of pixel A, green numerical value and blue values, B _r, B _g, B _bbe respectively the red value of pixel B, green numerical value and blue values, C _r, C _g, C _bbe respectively the red value of pixel C, green numerical value and blue values, D _r, D _g, D _bbe respectively the red value of pixel D, green numerical value and blue values, ABS is the poor absolute value of bracket moderate-element.

11. image compressing methods as claimed in claim 5, is characterized in that: in described step (B), in the time meeting following formula, judge that described 2x2 coding unit makes type as Sixth Man:

ABS(A _r,C _r)＜THD2,ABS(A _r,B _r)＜THD2,

ABS(A _g,C _g)＜THD2,ABS(A _g,B _g)＜THD2,

ABS(A _b,C _b)＜THD2,ABS(A _b,B _b)＜THD2,

ABS(A _r,C _r)+ABS(A _g,C _g)+ABS(A _b,C _b)≤

ABS(B _r,D _r)+ABS(B _g,D _g)+ABS(B _b,D _b),

ABS(A _r,C _r)+ABS(A _g,C _g)+ABS(A _b,C _b)≤

ABS(C _r,D _r)+ABS(C _g,D _g)+ABS(C _b,D _b),

ABS(A _r,B _r)+ABS(A _g,B _g)+ABS(A _b,B _b)≤

ABS(C _r,D _r)+ABS(C _g,D _g)+ABS(C _b,D _b),

ABS(A _r,B _r)+ABS(A _g,B _g)+ABS(A _b,B _b)≤

ABS(B _r,D _r)+ABS(B _g,D _g)+ABS(B _b,D _b),

Wherein, THD2 is the second threshold value, and A is described top left corner pixel, and B is described upper right corner pixel, and C is described lower left corner pixel, and D is described lower right corner pixel, A _r, A _g, A _bbe respectively the red value of pixel A, green numerical value and blue values, B _r, B _g, B _bbe respectively the red value of pixel B, green numerical value and blue values, C _r, C _g, C _bbe respectively the red value of pixel C, green numerical value and blue values, D _r, D _g, D _bbe respectively the red value of pixel D, green numerical value and blue values, ABS is the poor absolute value of bracket moderate-element.

12. image compressing methods as claimed in claim 5, is characterized in that: in described step (B), in the time meeting following formula, judge that described 2x2 coding unit is as the 7th artificial type:

ABS(A _r,C _r)＜THD2,ABS(C _r,D _r)＜THD2,

ABS(A _g,C _g)＜THD2,ABS(C _g,D _g)＜THD2,

ABS(A _b,C _b)＜THD2,ABS(C _b,D _b)＜THD2,

ABS(A _r,C _r)+ABS(A _g,C _g)+ABS(A _b,C _b)≤

ABS(B _r,D _r)+ABS(B _g,D _g)+ABS(B _b,D _b),

ABS(A _r,C _r)+ABS(A _g,C _g)+ABS(A _b,C _b)≤

ABS(A _r,B _r)+ABS(A _g,B _g)+ABS(A _b,B _b),

ABS(C _r,D _r)+ABS(C _g,D _g)+ABS(C _b,D _b)≤

ABS(A _r,B _r)+ABS(A _g,B _g)+ABS(A _b,B _b),

ABS(C _r,D _r)+ABS(C _g,D _g)+ABS(C _b,D _b)≤

ABS(B _r,D _r)+ABS(B _g,D _g)+ABS(B _b,D _b),

Wherein, THD2 is the second threshold value, and A is described top left corner pixel, and B is described upper right corner pixel, and C is described lower left corner pixel, and D is described lower right corner pixel, A _r, A _g, A _bbe respectively the red value of pixel A, green numerical value and blue values, B _r, B _g, B _bbe respectively the red value of pixel B, green numerical value and blue values, C _r, C _g, C _bbe respectively the red value of pixel C, green numerical value and blue values, D _r, D _g, D _bbe respectively the red value of pixel D, green numerical value and blue values, ABS is the poor absolute value of bracket moderate-element.

13. image compressing methods as claimed in claim 4, is characterized in that: in described 2x2 coding unit, every kind of color numerical value adopts 8 bit representations.

14. image compressing methods as claimed in claim 4, is characterized in that: in described 2x2 coding unit, every kind of color numerical value adopts 6 bit representations.

15. image compressing methods as described in claim 13 or 14, is characterized in that: in described step (B), in the time meeting following formula, judge that described 2x2 coding unit is as the first artificial type:

ABS(A _y,B _y)＜THDY1，ABS(C _y,D _y)＜THDY1

ABS(A _u,B _u)＜THDU1，ABS(C _u,D _u)＜THDU1

ABS(A _v,B _v)＜THDV1，ABS(C _v,D _v)＜THDV1

ABS(A _y,B _y)+ABS(A _v,B _v)+ABS(A _u,B _u)≤ABS(A _y,C _y)+ABS(A _v,C _v)+ABS(A _u,C _u)

ABS(A _y,B _y)+ABS(A _v,B _v)+ABS(A _u,B _u)≤ABS(D _y,B _y)+ABS(D _v,B _v)+ABS(D _u,B _u)

ABS(C _y,D _y)+ABS(C _v,D _v)+ABS(C _u,D _u)≤ABS(D _y,B _y)+ABS(D _v,B _v)+ABS(D _u,B _u)

ABS(C _y,D _y)+ABS(C _v,D _v)+ABS(C _u,D _u)≤ABS(A _y,C _y)+ABS(A _v,C _v)+ABS(A _u,C _u)

Wherein, ABS is the poor ABS function of two elements in bracket, and THDY1 is lightness threshold value 1, and THDU1 is the first colourity threshold value 1, THDV1 is the second colourity threshold value 1, and A is described top left corner pixel, and B is described upper right corner pixel, C is described lower left corner pixel, and D is described lower right corner pixel, A _y, A _u, A _vbe respectively lightness, the first colourity and second chromatic value of pixel A, B _y, B _u, B _vbe respectively lightness, the first colourity and second chromatic value of pixel B, C _y, C _u, C _vbe respectively lightness, the first colourity and the second chromatic value of pixel C, D _y, D _u, D _vbe respectively lightness, the first colourity and the second chromatic value of pixel D;

Wherein, described lightness, the first colourity and the second chromatic value carry out RGB to YUV color gamut conversion by following formula and obtain:

$\left[\begin{array}{c}Y\\ U\\ V\end{array}\right]=\left[\begin{array}{ccc}0.25& 0.5& 0.25\\ -0.5& 1.0& -0.5\\ -1.0& 0& 1.0\end{array}\right]\left[\begin{array}{c}r\\ g\\ b\end{array}\right],$

Wherein, r is the red value of a pixel, the green value that g is this pixel, the blue valve that b is this pixel, the lightness that Y is this pixel, the colourity that U and V are this pixel.

16. image compressing methods as described in claim 13 or 14, is characterized in that: in described step (B), in the time meeting following formula, judge that described 2x2 coding unit is as the second artificial type:

ABS(A _y,C _y)＜THDY1，ABS(B _y,D _y)＜THDY1

ABS(A _u,C _u)＜THDU1，ABS(B _u,D _u)＜THDU1

ABS(A _v,C _v)＜THDV1，ABS(B _v,D _v)＜THDV1

ABS(A _y,C _y)+ABS(A _v,C _v)+ABS(A _u,C _u)≤ABS(A _y,B _y)+ABS(A _v,B _v)+ABS(A _u,B _u)

ABS(A _y,C _y)+ABS(A _v,C _v)+ABS(A _u,C _u)≤ABS(C _y,D _y)+ABS(C _v,D _v)+ABS(C _u,D _u)

ABS(B _y,D _y)+ABS(B _v,D _v)+ABS(B _u,D _u)≤ABS(A _y,B _y)+ABS(A _v,B _v)+ABS(A _u,B _u)

ABS(B _y,D _y)+ABS(B _v,D _v)+ABS(B _u,D _u)≤ABS(D _y,C _y)+ABS(D _v,C _v)+ABS(D _u,C _u)

Wherein, ABS is the poor ABS function of two elements in bracket, and THDY1 is lightness threshold value 1, and THDU1 is the first colourity threshold value 1, THDV1 is the second colourity threshold value 1, and A is described top left corner pixel, and B is described upper right corner pixel, C is described lower left corner pixel, and D is described lower right corner pixel, A _y, A _u, A _vbe respectively lightness, the first colourity and second chromatic value of pixel A, B _y, B _u, B _vbe respectively lightness, the first colourity and second chromatic value of pixel B, C _y, C _u, C _vbe respectively lightness, the first colourity and the second chromatic value of pixel C, D _y, D _u, D _vbe respectively lightness, the first colourity and the second chromatic value of pixel D;

Wherein, described lightness, the first colourity and the second chromatic value carry out RGB to YUV color gamut conversion by following formula and obtain:

$\left[\begin{array}{c}Y\\ U\\ V\end{array}\right]=\left[\begin{array}{ccc}0.25& 0.5& 0.25\\ -0.5& 1.0& -0.5\\ -1.0& 0& 1.0\end{array}\right]\left[\begin{array}{c}r\\ g\\ b\end{array}\right],$

Wherein, r is the red value of a pixel, the green value that g is this pixel, the blue valve that b is this pixel, the lightness that Y is this pixel, the colourity that U and V are this pixel.

17. image compressing methods as described in claim 13 or 14, is characterized in that: in described step (B), in the time meeting following formula, judge that described 2x2 coding unit is as the 3rd artificial type:

ABS(C _y,B _y)＜THDY1，ABS(A _y,D _y)＜THDY1

ABS(C _u,B _u)＜THDU1，ABS(A _u,D _u)＜THDU1

ABS(C _v,B _v)＜THDV1，ABS(A _v,D _v)＜THDV1

ABS(C _y,B _y)+ABS(C _v,B _v)+ABS(C _u,B _u)≤ABS(A _y,B _y)+ABS(A _v,B _v)+ABS(A _u,B _u)

ABS(C _y,B _y)+ABS(C _v,B _v)+ABS(C _u,B _u)≤ABS(D _y,C _y)+ABS(D _v,C _v)+ABS(D _u,C _u)

ABS(A _y,D _y)+ABS(A _v,D _v)+ABS(A _u,D _u)≤ABS(A _y,B _y)+ABS(A _v,B _v)+ABS(A _u,B _u)

ABS(A _y,D _y)+ABS(A _v,D _v)+ABS(A _u,D _u)≤ABS(D _y,C _y)+ABS(D _v,C _v)+ABS(D _u,C _u)

Wherein, ABS is the poor ABS function of two elements in bracket, and THDY1 is lightness threshold value 1, and THDU1 is the first colourity threshold value 1, THDV1 is the second colourity threshold value 1, and A is described top left corner pixel, and B is described upper right corner pixel, C is described lower left corner pixel, and D is described lower right corner pixel, A _y, A _u, A _vbe respectively lightness, the first colourity and second chromatic value of pixel A, B _y, B _u, B _vbe respectively lightness, the first colourity and second chromatic value of pixel B, C _y, C _u, C _vbe respectively lightness, the first colourity and the second chromatic value of pixel C, D _y, D _u, D _vbe respectively lightness, the first colourity and the second chromatic value of pixel D;

Wherein, described lightness, the first colourity and the second chromatic value carry out RGB to YUV color gamut conversion by following formula and obtain:

$\left[\begin{array}{c}Y\\ U\\ V\end{array}\right]=\left[\begin{array}{ccc}0.25& 0.5& 0.25\\ -0.5& 1.0& -0.5\\ -1.0& 0& 1.0\end{array}\right]\left[\begin{array}{c}r\\ g\\ b\end{array}\right],$

Wherein, r is the red value of a pixel, the green value that g is this pixel, the blue valve that b is this pixel, the lightness that Y is this pixel, the colourity that U and V are this pixel.

18. image compressing methods as described in claim 13 or 14, is characterized in that: in described step (B), in the time meeting following formula, judge that described 2x2 coding unit is as the 4th artificial type:

ABS(D _y,B _y)＜THDY2，ABS(C _y,D _y)＜THDY2

ABS(D _u,B _u)＜THDU2，ABS(C _u,D _u)＜THDU2

ABS(D _v,B _v)＜THDV2，ABS(C _v,D _v)＜THDV2

ABS(D _y,B _y)+ABS(D _v,B _v)+ABS(D _u,B _u)≤ABS(A _y,C _y)+ABS(A _v,C _v)+ABS(A _u,C _u)

ABS(D _y,B _y)+ABS(D _v,B _v)+ABS(D _u,B _u)≤ABS(A _y,B _y)+ABS(A _v,B _v)+ABS(A _u,B _u)

ABS(D _y,C _y)+ABS(D _v,C _v)+ABS(D _u,C _u)≤ABS(A _y,C _y)+ABS(A _v,C _v)+ABS(A _u,C _u)

ABS(D _y,C _y)+ABS(D _v,C _v)+ABS(D _u,C _u)≤ABS(A _y,B _y)+ABS(A _v,B _v)+ABS(A _u,B _u)

Wherein, ABS is the poor ABS function of two elements in bracket, and THDY2 is lightness threshold value 2, and THDU2 is the first colourity threshold value 2, THDV2 is the second colourity threshold value 2, and A is described top left corner pixel, and B is described upper right corner pixel, C is described lower left corner pixel, and D is described lower right corner pixel, A _y, A _u, A _vbe respectively lightness, the first colourity and second chromatic value of pixel A, B _y, B _u, B _vbe respectively lightness, the first colourity and second chromatic value of pixel B, C _y, C _u, C _vbe respectively lightness, the first colourity and the second chromatic value of pixel C, D _y, D _u, D _vbe respectively lightness, the first colourity and the second chromatic value of pixel D;

Wherein, described lightness, the first colourity and the second chromatic value carry out RGB to YUV color gamut conversion by following formula and obtain:

$\left[\begin{array}{c}Y\\ U\\ V\end{array}\right]=\left[\begin{array}{ccc}0.25& 0.5& 0.25\\ -0.5& 1.0& -0.5\\ -1.0& 0& 1.0\end{array}\right]\left[\begin{array}{c}r\\ g\\ b\end{array}\right],$

Wherein, r is the red value of a pixel, the green value that g is this pixel, the blue valve that b is this pixel, the lightness that Y is this pixel, the colourity that U and V are this pixel.

19. image compressing methods as described in claim 13 or 14, is characterized in that: in described step (B), in the time meeting following formula, judge that described 2x2 coding unit is as the 5th artificial type:

ABS(D _y,B _y)＜THDY2，ABS(A _y,B _y)＜THDY2

ABS(D _u,B _u)＜THDU2，ABS(A _u,B _u)＜THDU2

ABS(D _v,B _v)＜THDV2，ABS(A _v,B _v)＜THDV2

ABS(D _y,B _y)+ABS(D _v,B _v)+ABS(D _u,B _u)≤ABS(A _y,C _y)+ABS(A _v,C _v)+ABS(A _u,C _u)

ABS(D _y,B _y)+ABS(D _v,B _v)+ABS(D _u,B _u)≤ABS(C _y,D _y)+ABS(C _v,D _v)+ABS(C _u,D _u)

ABS(A _y,B _y)+ABS(A _v,B _v)+ABS(A _u,B _u)≤ABS(A _y,C _y)+ABS(A _v,C _v)+ABS(A _u,C _u)

ABS(A _y,B _y)+ABS(A _v,B _v)+ABS(A _u,B _u)≤ABS(C _y,D _y)+ABS(C _v,D _v)+ABS(C _u,D _u)

Wherein, ABS is the poor ABS function of two elements in bracket, and THDY2 is lightness threshold value 2, and THDU2 is the first colourity threshold value 2, THDV2 is the second colourity threshold value 2, and A is described top left corner pixel, and B is described upper right corner pixel, C is described lower left corner pixel, and D is described lower right corner pixel, A _y, A _u, A _vbe respectively lightness, the first colourity and second chromatic value of pixel A, B _y, B _u, B _vbe respectively lightness, the first colourity and second chromatic value of pixel B, C _y, C _u, C _vbe respectively lightness, the first colourity and the second chromatic value of pixel C, D _y, D _u, D _vbe respectively lightness, the first colourity and the second chromatic value of pixel D;

Wherein, described lightness, the first colourity and the second chromatic value carry out RGB to YUV color gamut conversion by following formula and obtain:

$\left[\begin{array}{c}Y\\ U\\ V\end{array}\right]=\left[\begin{array}{ccc}0.25& 0.5& 0.25\\ -0.5& 1.0& -0.5\\ -1.0& 0& 1.0\end{array}\right]\left[\begin{array}{c}r\\ g\\ b\end{array}\right],$

Wherein, r is the red value of a pixel, the green value that g is this pixel, the blue valve that b is this pixel, the lightness that Y is this pixel, the colourity that U and V are this pixel.

20. image compressing methods as described in claim 13 or 14, is characterized in that: in described step (B), in the time meeting following formula, judge that described 2x2 coding unit makes type as Sixth Man:

ABS(A _y,B _y)＜THDY2，ABS(C _y,A _y)＜THDY2

ABS(A _u,B _u)＜THDU2，ABS(C _u,A _u)＜THDU2

ABS(A _v,B _v)＜THDV2，ABS(C _v,A _v)＜THDV2

ABS(A _y,B _y)+ABS(A _v,B _v)+ABS(A _u,B _u)≤ABS(D _y,C _y)+ABS(D _v,C _v)+ABS(D _u,C _u)

ABS(A _y,B _y)+ABS(A _v,B _v)+ABS(A _u,B _u)≤ABS(D _y,B _y)+ABS(D _v,B _v)+ABS(D _u,B _u)

ABS(A _y,C _y)+ABS(A _v,C _v)+ABS(A _u,C _u)≤ABS(D _y,C _y)+ABS(D _v,C _v)+ABS(D _u,C _u)

ABS(A _y,C _y)+ABS(A _v,C _v)+ABS(A _u,C _u)≤ABS(D _y,B _y)+ABS(D _v,B _v)+ABS(D _u,B _u)

Wherein, ABS is the poor ABS function of two elements in bracket, and THDY2 is lightness threshold value 2, and THDU2 is the first colourity threshold value 2, THDV2 is the second colourity threshold value 2, and A is described top left corner pixel, and B is described upper right corner pixel, C is described lower left corner pixel, and D is described lower right corner pixel, A _y, A _u, A _vbe respectively lightness, the first colourity and second chromatic value of pixel A, B _y, B _u, B _vbe respectively lightness, the first colourity and second chromatic value of pixel B, C _y, C _u, C _vbe respectively lightness, the first colourity and the second chromatic value of pixel C, D _y, D _u, D _vbe respectively lightness, the first colourity and the second chromatic value of pixel D;

Wherein, described lightness, the first colourity and the second chromatic value carry out RGB to YUV color gamut conversion by following formula and obtain:

$\left[\begin{array}{c}Y\\ U\\ V\end{array}\right]=\left[\begin{array}{ccc}0.25& 0.5& 0.25\\ -0.5& 1.0& -0.5\\ -1.0& 0& 1.0\end{array}\right]\left[\begin{array}{c}r\\ g\\ b\end{array}\right],$

Wherein, r is the red value of a pixel, the green value that g is this pixel, the blue valve that b is this pixel, the lightness that Y is this pixel, the colourity that U and V are this pixel.

21. image compressing methods as described in claim 13 or 14, is characterized in that: in described step (B), in the time meeting following formula, judge that described 2x2 coding unit is as the 7th artificial type:

ABS(A _y,C _y)＜THDY2，ABS(C _y,D _y)＜THDY2

ABS(A _u,C _u)＜THDU2，ABS(C _u,D _u)＜THDU2

ABS(A _v,C _v)＜THDV2，ABS(C _v,D _v)＜THDV2

ABS(A _y,C _y)+ABS(A _v,C _v)+ABS(A _u,C _u)≤ABS(B _y,D _y)+ABS(B _v,D _v)+ABS(B _u,D _u)

ABS(A _y,C _y)+ABS(A _v,C _v)+ABS(A _u,C _u)≤ABS(A _y,B _y)+ABS(A _v,B _v)+ABS(A _u,B _u)

ABS(D _y,C _y)+ABS(D _v,C _v)+ABS(D _u,C _u)≤ABS(B _y,D _y)+ABS(B _v,D _v)+ABS(B _u,D _u)

ABS(D _y,C _y)+ABS(D _v,C _v)+ABS(D _u,C _u)≤ABS(A _y,B _y)+ABS(A _v,B _v)+ABS(A _u,B _u)

Wherein, ABS is the poor ABS function of two elements in bracket, and THDY2 is lightness threshold value 2, and THDU2 is the first colourity threshold value 2, THDV2 is the second colourity threshold value 2, and A is described top left corner pixel, and B is described upper right corner pixel, C is described lower left corner pixel, and D is described lower right corner pixel, A _y, A _u, A _vbe respectively lightness, the first colourity and second chromatic value of pixel A, B _y, B _u, B _vbe respectively lightness, the first colourity and second chromatic value of pixel B, C _y, C _u, C _vbe respectively lightness, the first colourity and the second chromatic value of pixel C, D _y, D _u, D _vbe respectively lightness, the first colourity and the second chromatic value of pixel D;

Wherein, described lightness, the first colourity and the second chromatic value carry out RGB to YUV color gamut conversion by following formula and obtain:

$\left[\begin{array}{c}Y\\ U\\ V\end{array}\right]=\left[\begin{array}{ccc}0.25& 0.5& 0.25\\ -0.5& 1.0& -0.5\\ -1.0& 0& 1.0\end{array}\right]\left[\begin{array}{c}r\\ g\\ b\end{array}\right],$

Wherein, r is the red value of a pixel, the green value that g is this pixel, the blue valve that b is this pixel, the lightness that Y is this pixel, the colourity that U and V are this pixel.

22. image compressing methods as claimed in claim 13, is characterized in that: in described step (B), in the time meeting following formula, judge that described 2x2 coding unit is as the 8th artificial type:

temp1＝ABS(A _y,B _y)+ABS(A _v,B _v)+ABS(A _u,B _u)

temp2＝ABS(A _y,C _y)+ABS(A _v,C _v)+ABS(A _u,C _u)

temp3＝ABS(A _y,D _y)+ABS(A _v,D _v)+ABS(A _u,D _u)

temp4＝ABS(D _y,B _y)+ABS(D _v,B _v)+ABS(D _u,B _u)

temp5＝ABS(C _y,B _y)+ABS(C _v,B _v)+ABS(C _u,B _u)

temp6＝ABS(C _y,D _y)+ABS(C _v,D _v)+ABS(C _u,D _u)

MIN(temp1,temp2,temp3,temp4,temp5,temp6)＝temp1

ABS(A _y,B _y)＜THDY4

ABS(A _v,B _v)＜THDV4

ABS(A _u,B _u)＜THDU4

ABS (C _y, D _y) > THDY3 or ABS (C _v, D _v) > THDV3 or ABS (C _u, D _u) > THDU3

Wherein, ABS is the poor ABS function of two elements in bracket, and THDY3 is lightness threshold value 3, THDU3 is the first colourity threshold value 3, THDV3 is the second colourity threshold value 3, and THDY4 is lightness threshold value 4, and THDU4 is the first colourity threshold value 4, THDV4 is the second colourity threshold value 4, A is described top left corner pixel, and B is described upper right corner pixel, and C is described lower left corner pixel, D is described lower right corner pixel, A _y, A _u, A _vbe respectively lightness, the first colourity and second chromatic value of pixel A, B _y, B _u, B _vbe respectively lightness, the first colourity and second chromatic value of pixel B, C _y, C _u, C _vbe respectively lightness, the first colourity and the second chromatic value of pixel C, D _y, D _u, D _vbe respectively lightness, the first colourity and the second chromatic value of pixel D;

Wherein, described lightness, the first colourity and the second chromatic value carry out RGB to YUV color gamut conversion by following formula and obtain:

$\left[\begin{array}{c}Y\\ U\\ V\end{array}\right]=\left[\begin{array}{ccc}0.25& 0.5& 0.25\\ -0.5& 1.0& -0.5\\ -1.0& 0& 1.0\end{array}\right]\left[\begin{array}{c}r\\ g\\ b\end{array}\right],$

Wherein, r is the red value of a pixel, the green value that g is this pixel, the blue valve that b is this pixel, the lightness that Y is this pixel, the colourity that U and V are this pixel.

23. image compressing methods as claimed in claim 13, is characterized in that: in described step (B), in the time meeting following formula, judge that described 2x2 coding unit is as the 9th artificial type:

temp1＝ABS(A _y,B _y)+ABS(A _v,B _v)+ABS(A _u,B _u)

temp2＝ABS(A _y,C _y)+ABS(A _v,C _v)+ABS(A _u,C _u)

temp3＝ABS(A _y,D _y)+ABS(A _v,D _v)+ABS(A _u,D _u)

temp4＝ABS(D _y,B _y)+ABS(D _v,B _v)+ABS(D _u,B _u)

temp5＝ABS(C _y,B _y)+ABS(C _v,B _v)+ABS(C _u,B _u)

temp6＝ABS(C _y,D _y)+ABS(C _v,D _v)+ABS(C _u,D _u)

MIN(temp1,temp2,temp3,temp4,temp5,temp6)＝temp6

ABS(C _y,D _y)＜THDY4

ABS(C _v,D _v)＜THDV4

ABS(C _u,D _u)＜THDU4

ABS (A _y, B _y) > THDY3 or ABS (A _v, B _v) > THDV3 or ABS (A _u, B _u) > THDU3

Wherein, ABS is the poor ABS function of two elements in bracket, and THDY3 is lightness threshold value 3, THDU3 is the first colourity threshold value 3, THDV3 is the second colourity threshold value 3, and THDY4 is lightness threshold value 4, and THDU4 is the first colourity threshold value 4, THDV4 is the second colourity threshold value 4, A is described top left corner pixel, and B is described upper right corner pixel, and C is described lower left corner pixel, D is described lower right corner pixel, A _y, A _u, A _vbe respectively lightness, the first colourity and second chromatic value of pixel A, B _y, B _u, B _vbe respectively lightness, the first colourity and second chromatic value of pixel B, C _y, C _u, C _vbe respectively lightness, the first colourity and the second chromatic value of pixel C, D _y, D _u, D _vbe respectively lightness, the first colourity and the second chromatic value of pixel D;

Wherein, described lightness, the first colourity and the second chromatic value carry out RGB to YUV color gamut conversion by following formula and obtain:

$\left[\begin{array}{c}Y\\ U\\ V\end{array}\right]=\left[\begin{array}{ccc}0.25& 0.5& 0.25\\ -0.5& 1.0& -0.5\\ -1.0& 0& 1.0\end{array}\right]\left[\begin{array}{c}r\\ g\\ b\end{array}\right],$

Wherein, r is the red value of a pixel, the green value that g is this pixel, the blue valve that b is this pixel, the lightness that Y is this pixel, the colourity that U and V are this pixel.

24. image compressing methods as claimed in claim 13, is characterized in that: in described step (B), in the time meeting following formula, judge that described 2x2 coding unit is as the tenth artificial type:

temp1＝ABS(A _y,B _y)+ABS(A _v,B _v)+ABS(A _u,B _u)

temp2＝ABS(A _y,C _y)+ABS(A _v,C _v)+ABS(A _u,C _u)

temp3＝ABS(A _y,D _y)+ABS(A _v,D _v)+ABS(A _u,D _u)

temp4＝ABS(D _y,B _y)+ABS(D _v,B _v)+ABS(D _u,B _u)

temp5＝ABS(C _y,B _y)+ABS(C _v,B _v)+ABS(C _u,B _u)

temp6＝ABS(C _y,D _y)+ABS(C _v,D _v)+ABS(C _u,D _u)

MIN(temp1,temp2,temp3,temp4,temp5,temp6)＝temp2

ABS(A _y,C _y)＜THDY4

ABS(A _v,C _v)＜THDV4

ABS(A _u,C _u)＜THDU4

ABS (B _y, D _y) > THDY3 or ABS (B _v, D _v) > THDV3 or ABS (B _u, D _u) > THDU3

Wherein, ABS is the poor ABS function of two elements in bracket, and THDY3 is lightness threshold value 3, THDU3 is the first colourity threshold value 3, THDV3 is the second colourity threshold value 3, and THDY4 is lightness threshold value 4, and THDU4 is the first colourity threshold value 4, THDV4 is the second colourity threshold value 4, A is described top left corner pixel, and B is described upper right corner pixel, and C is described lower left corner pixel, D is described lower right corner pixel, A _y, A _u, A _vbe respectively lightness, the first colourity and second chromatic value of pixel A, B _y, B _u, B _vbe respectively lightness, the first colourity and second chromatic value of pixel B, C _y, C _u, C _vbe respectively lightness, the first colourity and the second chromatic value of pixel C, D _y, D _u, D _vbe respectively lightness, the first colourity and the second chromatic value of pixel D;

Wherein, described lightness, the first colourity and the second chromatic value carry out RGB to YUV color gamut conversion by following formula and obtain:

$\left[\begin{array}{c}Y\\ U\\ V\end{array}\right]=\left[\begin{array}{ccc}0.25& 0.5& 0.25\\ -0.5& 1.0& -0.5\\ -1.0& 0& 1.0\end{array}\right]\left[\begin{array}{c}r\\ g\\ b\end{array}\right],$

Wherein, r is the red value of a pixel, the green value that g is this pixel, the blue valve that b is this pixel, the lightness that Y is this pixel, the colourity that U and V are this pixel.

25. image compressing methods as claimed in claim 13, is characterized in that: in described step (B), in the time meeting following formula, judge that described 2x2 coding unit is as the 11 artificial type:

temp1＝ABS(A _y,B _y)+ABS(A _v,B _v)+ABS(A _u,B _u)

temp2＝ABS(A _y,C _y)+ABS(A _v,C _v)+ABS(A _u,C _u)

temp3＝ABS(A _y,D _y)+ABS(A _v,D _v)+ABS(A _u,D _u)

temp4＝ABS(D _y,B _y)+ABS(D _v,B _v)+ABS(D _u,B _u)

temp5＝ABS(C _y,B _y)+ABS(C _v,B _v)+ABS(C _u,B _u)

temp6＝ABS(C _y,D _y)+ABS(C _v,D _v)+ABS(C _u,D _u)

MIN(temp1,temp2,temp3,temp4,temp5,temp6)＝temp4

ABS(D _y,B _y)＜THDY4

ABS(D _v,B _v)＜THDV4

ABS(D _u,B _u)＜THDU4

ABS (C _y, A _y) > THDY3 or ABS (C _v, A _v) > THDV3 or ABS (C _u, A _u) > THDU3

Wherein, ABS is the poor ABS function of two elements in bracket, and THDY3 is lightness threshold value 3, THDU3 is the first colourity threshold value 3, THDV3 is the second colourity threshold value 3, and THDY4 is lightness threshold value 4, and THDU4 is the first colourity threshold value 4, THDV4 is the second colourity threshold value 4, A is described top left corner pixel, and B is described upper right corner pixel, and C is described lower left corner pixel, D is described lower right corner pixel, A _y, A _u, A _vbe respectively lightness, the first colourity and second chromatic value of pixel A, B _y, B _u, B _vbe respectively lightness, the first colourity and second chromatic value of pixel B, C _y, C _u, C _vbe respectively lightness, the first colourity and the second chromatic value of pixel C, D _y, D _u, D _vbe respectively lightness, the first colourity and the second chromatic value of pixel D;

Wherein, described lightness, the first colourity and the second chromatic value carry out RGB to YUV color gamut conversion by following formula and obtain:

$\left[\begin{array}{c}Y\\ U\\ V\end{array}\right]=\left[\begin{array}{ccc}0.25& 0.5& 0.25\\ -0.5& 1.0& -0.5\\ -1.0& 0& 1.0\end{array}\right]\left[\begin{array}{c}r\\ g\\ b\end{array}\right],$

Wherein, r is the red value of a pixel, the green value that g is this pixel, the blue valve that b is this pixel, the lightness that Y is this pixel, the colourity that U and V are this pixel.

26. image compressing methods as claimed in claim 13, is characterized in that: in described step (B), in the time meeting following formula, judge that described 2x2 coding unit is as the 12 artificial type:

temp1＝ABS(A _y,B _y)+ABS(A _v,B _v)+ABS(A _u,B _u)

temp2＝ABS(A _y,C _y)+ABS(A _v,C _v)+ABS(A _u,C _u)

temp3＝ABS(A _y,D _y)+ABS(A _v,D _v)+ABS(A _u,D _u)

temp4＝ABS(D _y,B _y)+ABS(D _v,B _v)+ABS(D _u,B _u)

temp5＝ABS(C _y,B _y)+ABS(C _v,B _v)+ABS(C _u,B _u)

temp6＝ABS(C _y,D _y)+ABS(C _v,D _v)+ABS(C _u,D _u)

MIN(temp1,temp2,temp3,temp4,temp5,temp6)＝temp3

ABS(A _y,D _y)＜THDY4

ABS(A _v,D _v)＜THDV4

ABS(A _u,D _u)＜THDU4

ABS (C _y, B _y) > THDY3 or ABS (C _v, B _v) > THDV3 or ABS (C _u, B _u) > THDU3

Wherein, ABS is the poor ABS function of two elements in bracket, and THDY3 is lightness threshold value 3, THDU3 is the first colourity threshold value 3, THDV3 is the second colourity threshold value 3, and THDY4 is lightness threshold value 4, and THDU4 is the first colourity threshold value 4, THDV4 is the second colourity threshold value 4, A is described top left corner pixel, and B is described upper right corner pixel, and C is described lower left corner pixel, D is described lower right corner pixel, A _y, A _u, A _vbe respectively lightness, the first colourity and second chromatic value of pixel A, B _y, B _u, B _vbe respectively lightness, the first colourity and second chromatic value of pixel B, C _y, C _u, C _vbe respectively lightness, the first colourity and the second chromatic value of pixel C, D _y, D _u, D _vbe respectively lightness, the first colourity and the second chromatic value of pixel D;

Wherein, described lightness, the first colourity and the second chromatic value carry out RGB to YUV color gamut conversion by following formula and obtain:

$\left[\begin{array}{c}Y\\ U\\ V\end{array}\right]=\left[\begin{array}{ccc}0.25& 0.5& 0.25\\ -0.5& 1.0& -0.5\\ -1.0& 0& 1.0\end{array}\right]\left[\begin{array}{c}r\\ g\\ b\end{array}\right],$

Wherein, r is the red value of a pixel, the green value that g is this pixel, the blue valve that b is this pixel, the lightness that Y is this pixel, the colourity that U and V are this pixel.

27. image compressing methods as claimed in claim 13, is characterized in that: in described step (B), in the time meeting following formula, judge that described 2x2 coding unit is as the 13 artificial type:

temp1＝ABS(A _y,B _y)+ABS(A _v,B _v)+ABS(A _u,B _u)

temp2＝ABS(A _y,C _y)+ABS(A _v,C _v)+ABS(A _u,C _u)

temp3＝ABS(A _y,D _y)+ABS(A _v,D _v)+ABS(A _u,D _u)

temp4＝ABS(D _y,B _y)+ABS(D _v,B _v)+ABS(D _u,B _u)

temp5＝ABS(C _y,B _y)+ABS(C _v,B _v)+ABS(C _u,B _u)

temp6＝ABS(C _y,D _y)+ABS(C _v,D _v)+ABS(C _u,D _u)

MIN(temp1,temp2,temp3,temp4,temp5,temp6)＝temp5

ABS(C _y,B _y)＜THDY4

ABS(C _v,B _v)＜THDV4

ABS(C _u,B _u)＜THDU4

ABS (A _y, D _y) > THDY3 or ABS (A _v, D _v) > THDV3 or ABS (A _u, D _u) > THDU3

Wherein, ABS is the poor ABS function of two elements in bracket, and THDY3 is lightness threshold value 3, THDU3 is the first colourity threshold value 3, THDV3 is the second colourity threshold value 3, and THDY4 is lightness threshold value 4, and THDU4 is the first colourity threshold value 4, THDV4 is the second colourity threshold value 4, A is described top left corner pixel, and B is described upper right corner pixel, and C is described lower left corner pixel, D is described lower right corner pixel, A _y, A _u, A _vbe respectively lightness, the first colourity and second chromatic value of pixel A, B _y, B _u, B _vbe respectively lightness, the first colourity and second chromatic value of pixel B, C _y, C _u, C _vbe respectively lightness, the first colourity and the second chromatic value of pixel C, D _y, D _u, D _vbe respectively lightness, the first colourity and the second chromatic value of pixel D;

Wherein, described lightness, the first colourity and the second chromatic value carry out RGB to YUV color gamut conversion by following formula and obtain:

$\left[\begin{array}{c}Y\\ U\\ V\end{array}\right]=\left[\begin{array}{ccc}0.25& 0.5& 0.25\\ -0.5& 1.0& -0.5\\ -1.0& 0& 1.0\end{array}\right]\left[\begin{array}{c}r\\ g\\ b\end{array}\right],$

Wherein, r is the red value of a pixel, the green value that g is this pixel, the blue valve that b is this pixel, the lightness that Y is this pixel, the colourity that U and V are this pixel.

28. image compressing methods as claimed in claim 14, is characterized in that: in described step (B), in the time meeting following formula, judge that described 2x2 coding unit is as the 8th artificial type:

temp1＝ABS(A _y,B _y)+ABS(A _v,B _v)+ABS(A _u,B _u)

temp2＝ABS(A _y,C _y)+ABS(A _v,C _v)+ABS(A _u,C _u)

temp3＝ABS(A _y,D _y)+ABS(A _v,D _v)+ABS(A _u,D _u)

temp4＝ABS(D _y,B _y)+ABS(D _v,B _v)+ABS(D _u,B _u)

temp5＝ABS(C _y,B _y)+ABS(C _v,B _v)+ABS(C _u,B _u)

temp6＝ABS(C _y,D _y)+ABS(C _v,D _v)+ABS(C _u,D _u)

MIN(temp1,temp2,temp3,temp4,temp5,temp6)＝temp1

ABS(A _y,B _y)＜THDY4

ABS(A _v,B _v)＜THDV4

ABS(A _u,B _u)＜THDU4

Wherein, ABS is the poor ABS function of two elements in bracket, and THDY4 is lightness threshold value 4, and THDU4 is the first colourity threshold value 4, THDV4 is the second colourity threshold value 4, and A is described top left corner pixel, and B is described upper right corner pixel, C is described lower left corner pixel, and D is described lower right corner pixel, A _y, A _u, A _vbe respectively lightness, the first colourity and second chromatic value of pixel A, B _y, B _u, B _vbe respectively lightness, the first colourity and second chromatic value of pixel B, C _y, C _u, C _vbe respectively lightness, the first colourity and the second chromatic value of pixel C, D _y, D _u, D _vbe respectively lightness, the first colourity and the second chromatic value of pixel D;

Wherein, described lightness, the first colourity and the second chromatic value carry out RGB to YUV color gamut conversion by following formula and obtain:

$\left[\begin{array}{c}Y\\ U\\ V\end{array}\right]=\left[\begin{array}{ccc}0.25& 0.5& 0.25\\ -0.5& 1.0& -0.5\\ -1.0& 0& 1.0\end{array}\right]\left[\begin{array}{c}r\\ g\\ b\end{array}\right],$

Wherein, r is the red value of a pixel, the green value that g is this pixel, the blue valve that b is this pixel, the lightness that Y is this pixel, the colourity that U and V are this pixel.

29. image compressing methods as claimed in claim 14, is characterized in that: in described step (B), in the time meeting following formula, judge that described 2x2 coding unit is as the 9th artificial type:

temp1＝ABS(A _y,B _y)+ABS(A _v,B _v)+ABS(A _u,B _u)

temp2＝ABS(A _y,C _y)+ABS(A _v,C _v)+ABS(A _u,C _u)

temp3＝ABS(A _y,D _y)+ABS(A _v,D _v)+ABS(A _u,D _u)

temp4＝ABS(D _y,B _y)+ABS(D _v,B _v)+ABS(D _u,B _u)

temp5＝ABS(C _y,B _y)+ABS(C _v,B _v)+ABS(C _u,B _u)

temp6＝ABS(C _y,D _y)+ABS(C _v,D _v)+ABS(C _u,D _u)

MIN(temp1,temp2,temp3,temp4,temp5,temp6)＝temp6

ABS(C _y,D _y)＜THDY4

ABS(C _v,D _v)＜THDV4

ABS(C _u,D _u)＜THDU4

Wherein, ABS is the poor ABS function of two elements in bracket, and THDY4 is lightness threshold value 4, and THDU4 is the first colourity threshold value 4, THDV4 is the second colourity threshold value 4, and A is described top left corner pixel, and B is described upper right corner pixel, C is described lower left corner pixel, and D is described lower right corner pixel, A _y, A _u, A _vbe respectively lightness, the first colourity and second chromatic value of pixel A, B _y, B _u, B _vbe respectively lightness, the first colourity and second chromatic value of pixel B, C _y, C _u, C _vbe respectively lightness, the first colourity and the second chromatic value of pixel C, D _y, D _u, D _vbe respectively lightness, the first colourity and the second chromatic value of pixel D;

Wherein, described lightness, the first colourity and the second chromatic value carry out RGB to YUV color gamut conversion by following formula and obtain:

$\left[\begin{array}{c}Y\\ U\\ V\end{array}\right]=\left[\begin{array}{ccc}0.25& 0.5& 0.25\\ -0.5& 1.0& -0.5\\ -1.0& 0& 1.0\end{array}\right]\left[\begin{array}{c}r\\ g\\ b\end{array}\right],$

Wherein, r is the red value of a pixel, the green value that g is this pixel, the blue valve that b is this pixel, the lightness that Y is this pixel, the colourity that U and V are this pixel.

30. image compressing methods as claimed in claim 14, is characterized in that: in described step (B), in the time meeting following formula, judge that described 2x2 coding unit is as the tenth artificial type:

temp1＝ABS(A _y,B _y)+ABS(A _v,B _v)+ABS(A _u,B _u)

temp2＝ABS(A _y,C _y)+ABS(A _v,C _v)+ABS(A _u,C _u)

temp3＝ABS(A _y,D _y)+ABS(A _v,D _v)+ABS(A _u,D _u)

temp4＝ABS(D _y,B _y)+ABS(D _v,B _v)+ABS(D _u,B _u)

temp5＝ABS(C _y,B _y)+ABS(C _v,B _v)+ABS(C _u,B _u)

temp6＝ABS(C _y,D _y)+ABS(C _v,D _v)+ABS(C _u,D _u)

MIN(temp1,temp2,temp3,temp4,temp5,temp6)＝temp2

ABS(A _y,C _y)＜THDY4

ABS(A _v,C _v)＜THDV4

ABS(A _u,C _u)＜THDU4

Wherein, ABS is the poor ABS function of two elements in bracket, and THDY4 is lightness threshold value 4, and THDU4 is the first colourity threshold value 4, THDV4 is the second colourity threshold value 4, and A is described top left corner pixel, and B is described upper right corner pixel, C is described lower left corner pixel, and D is described lower right corner pixel, A _y, A _u, A _vbe respectively lightness, the first colourity and second chromatic value of pixel A, B _y, B _u, B _vbe respectively lightness, the first colourity and second chromatic value of pixel B, C _y, C _u, C _vbe respectively lightness, the first colourity and the second chromatic value of pixel C, D _y, D _u, D _vbe respectively lightness, the first colourity and the second chromatic value of pixel D;

Wherein, described lightness, the first colourity and the second chromatic value carry out RGB to YUV color gamut conversion by following formula and obtain:

$\left[\begin{array}{c}Y\\ U\\ V\end{array}\right]=\left[\begin{array}{ccc}0.25& 0.5& 0.25\\ -0.5& 1.0& -0.5\\ -1.0& 0& 1.0\end{array}\right]\left[\begin{array}{c}r\\ g\\ b\end{array}\right],$

Wherein, r is the red value of a pixel, the green value that g is this pixel, the blue valve that b is this pixel, the lightness that Y is this pixel, the colourity that U and V are this pixel.

31. image compressing methods as claimed in claim 14, is characterized in that: in described step (B), in the time meeting following formula, judge that described 2x2 coding unit is as the 11 artificial type:

temp1＝ABS(A _y,B _y)+ABS(A _v,B _v)+ABS(A _u,B _u)

temp2＝ABS(A _y,C _y)+ABS(A _v,C _v)+ABS(A _u,C _u)

temp3＝ABS(A _y,D _y)+ABS(A _v,D _v)+ABS(A _u,D _u)

temp4＝ABS(D _y,B _y)+ABS(D _v,B _v)+ABS(D _u,B _u)

temp5＝ABS(C _y,B _y)+ABS(C _v,B _v)+ABS(C _u,B _u)

temp6＝ABS(C _y,D _y)+ABS(C _v,D _v)+ABS(C _u,D _u)

MIN(temp1,temp2,temp3,temp4,temp5,temp6)＝temp4

ABS(D _y,B _y)＜THDY4

ABS(D _v,B _v)＜THDV4

ABS(D _u,B _u)＜THDU4

Wherein, ABS is the poor ABS function of two elements in bracket, and THDY4 is lightness threshold value 4, and THDU4 is the first colourity threshold value 4, THDV4 is the second colourity threshold value 4, and A is described top left corner pixel, and B is described upper right corner pixel, C is described lower left corner pixel, and D is described lower right corner pixel, A _y, A _u, A _vbe respectively lightness, the first colourity and second chromatic value of pixel A, B _y, B _u, B _vbe respectively lightness, the first colourity and second chromatic value of pixel B, C _y, C _u, C _vbe respectively lightness, the first colourity and the second chromatic value of pixel C, D _y, D _u, D _vbe respectively lightness, the first colourity and the second chromatic value of pixel D;

Wherein, described lightness, the first colourity and the second chromatic value carry out RGB to YUV color gamut conversion by following formula and obtain:

$\left[\begin{array}{c}Y\\ U\\ V\end{array}\right]=\left[\begin{array}{ccc}0.25& 0.5& 0.25\\ -0.5& 1.0& -0.5\\ -1.0& 0& 1.0\end{array}\right]\left[\begin{array}{c}r\\ g\\ b\end{array}\right],$

Wherein, r is the red value of a pixel, the green value that g is this pixel, the blue valve that b is this pixel, the lightness that Y is this pixel, the colourity that U and V are this pixel.

32. image compressing methods as claimed in claim 14, is characterized in that: in described step (B), in the time meeting following formula, judge that described 2x2 coding unit is as the 12 artificial type:

temp1＝ABS(A _y,B _y)+ABS(A _v,B _v)+ABS(A _u,B _u)

temp2＝ABS(A _y,C _y)+ABS(A _v,C _v)+ABS(A _u,C _u)

temp3＝ABS(A _y,D _y)+ABS(A _v,D _v)+ABS(A _u,D _u)

temp4＝ABS(D _y,B _y)+ABS(D _v,B _v)+ABS(D _u,B _u)

temp5＝ABS(C _y,B _y)+ABS(C _v,B _v)+ABS(C _u,B _u)

temp6＝ABS(C _y,D _y)+ABS(C _v,D _v)+ABS(C _u,D _u)

MIN(temp1,temp2,temp3,temp4,temp5,temp6)＝temp3

ABS(A _y,D _y)＜THDY4

ABS(A _v,D _v)＜THDV4

ABS(A _u,D _u)＜THDU4

Wherein, ABS is the poor ABS function of two elements in bracket, and THDY4 is lightness threshold value 4, and THDU4 is the first colourity threshold value 4, THDV4 is the second colourity threshold value 4, and A is described top left corner pixel, and B is described upper right corner pixel, C is described lower left corner pixel, and D is described lower right corner pixel, A _y, A _u, A _vbe respectively lightness, the first colourity and second chromatic value of pixel A, B _y, B _u, B _vbe respectively lightness, the first colourity and second chromatic value of pixel B, C _y, C _u, C _vbe respectively lightness, the first colourity and the second chromatic value of pixel C, D _y, D _u, D _vbe respectively lightness, the first colourity and the second chromatic value of pixel D;

Wherein, described lightness, the first colourity and the second chromatic value carry out RGB to YUV color gamut conversion by following formula and obtain:

$\left[\begin{array}{c}Y\\ U\\ V\end{array}\right]=\left[\begin{array}{ccc}0.25& 0.5& 0.25\\ -0.5& 1.0& -0.5\\ -1.0& 0& 1.0\end{array}\right]\left[\begin{array}{c}r\\ g\\ b\end{array}\right],$

Wherein, r is the red value of a pixel, the green value that g is this pixel, the blue valve that b is this pixel, the lightness that Y is this pixel, the colourity that U and V are this pixel.

33. image compressing methods as claimed in claim 14, is characterized in that: in described step (B), in the time meeting following formula, judge that described 2x2 coding unit is as the 13 artificial type:

temp1＝ABS(A _y,B _y)+ABS(A _v,B _v)+ABS(A _u,B _u)

temp2＝ABS(A _y,C _y)+ABS(A _v,C _v)+ABS(A _u,C _u)

temp3＝ABS(A _y,D _y)+ABS(A _v,D _v)+ABS(A _u,D _u)

temp4＝ABS(D _y,B _y)+ABS(D _v,B _v)+ABS(D _u,B _u)

temp5＝ABS(C _y,B _y)+ABS(C _v,B _v)+ABS(C _u,B _u)

temp6＝ABS(C _y,D _y)+ABS(C _v,D _v)+ABS(C _u,D _u)

MIN(temp1,temp2,temp3,temp4,temp5,temp6)＝temp5

ABS(C _y,B _y)＜THDY4

ABS(C _v,B _v)＜THDV4

ABS(C _u,B _u)＜THDU4

Wherein, ABS is the poor ABS function of two elements in bracket, and THDY4 is lightness threshold value 4, and THDU4 is the first colourity threshold value 4, THDV4 is the second colourity threshold value 4, and A is described top left corner pixel, and B is described upper right corner pixel, C is described lower left corner pixel, and D is described lower right corner pixel, A _y, A _u, A _vbe respectively lightness, the first colourity and second chromatic value of pixel A, B _y, B _u, B _vbe respectively lightness, the first colourity and second chromatic value of pixel B, C _y, C _u, C _vbe respectively lightness, the first colourity and the second chromatic value of pixel C, D _y, D _u, D _vbe respectively lightness, the first colourity and the second chromatic value of pixel D;

Wherein, described lightness, the first colourity and the second chromatic value carry out RGB to YUV color gamut conversion by following formula and obtain:

$\left[\begin{array}{c}Y\\ U\\ V\end{array}\right]=\left[\begin{array}{ccc}0.25& 0.5& 0.25\\ -0.5& 1.0& -0.5\\ -1.0& 0& 1.0\end{array}\right]\left[\begin{array}{c}r\\ g\\ b\end{array}\right],$

Wherein, r is the red value of a pixel, the green value that g is this pixel, the blue valve that b is this pixel, the lightness that Y is this pixel, the colourity that U and V are this pixel.

34. image compressing methods as described in claim 5,13 or 14, is characterized in that: in step (D), by carrying out RGB to YUV color gamut conversion, to obtain described 2x2 gamut conversion unit, described RGB to YUV color gamut conversion is shown with following formula table:

$\left[\begin{array}{c}Y\\ U\\ V\end{array}\right]=\left[\begin{array}{ccc}0.25& 0.5& 0.25\\ -0.5& 1.0& -0.5\\ -1.0& 0& 1.0\end{array}\right]\left[\begin{array}{c}r\\ g\\ b\end{array}\right],$

Wherein, r is the red value of a pixel, g is the green value of this pixel, b is the blue valve of this pixel, Y is the lightness of this pixel, U and V are the colourity of this pixel, and described 2x2 gamut conversion unit is divided into lightness 2x2 gamut conversion unit (Y), the first colourity 2x2 gamut conversion unit (U) and the second colourity 2x2 gamut conversion unit (V).

35. image compressing methods as claimed in claim 34, is characterized in that: in step (E), described discrete cosine transform is shown with following formula table:

$\left[\begin{array}{c}E\\ F\\ G\\ H\end{array}\right]=0.25\&times;\left[\begin{array}{cccc}1& 1& 1& 1\\ 1& -1& 1& -1\\ 1& 1& -1& -1\\ 1& -1& -1& 1\end{array}\right]\left[\begin{array}{c}\stackrel{\&OverBar;}{A}\\ \stackrel{\&OverBar;}{B}\\ \stackrel{\&OverBar;}{C}\\ \stackrel{\&OverBar;}{D}\end{array}\right],$

Wherein, for the upper left corner value of described 2x2 gamut conversion unit, for the upper right corner value of described 2x2 gamut conversion unit, for the lower left corner value of described 2x2 gamut conversion unit, for the lower right corner value of described 2x2 gamut conversion unit, E element is the upper left corner value of described 2x2 frequency domain unit, F element is the upper right corner value of described 2x2 frequency domain unit, G element is the lower left corner value of described 2x2 frequency domain unit, H element is the lower right corner value of described 2x2 frequency domain unit, and described 2x2 frequency domain unit is divided into lightness 2x2 frequency domain unit, the first colourity 2x2 frequency domain unit and the second colourity 2x2 frequency domain unit.

36. image compressing methods as described in claim 5 or 14, is characterized in that: between described step (E) and step (F), also comprise step:

(H) described 2x2 frequency domain unit is divided into the first natural type or the second nature type, wherein, when F element and G element in described the first colourity 2x2 frequency domain unit (U) meet following formula:

max(ABS(F,0),ABS(G,0))≤THD3，

And F element and G element in described the second colourity 2x2 frequency domain unit (V) meet following formula:

max(ABS(F,0),ABS(G,0))≤THD4，

Judge that this 2x2 frequency domain unit is as described the first natural type, otherwise, judge that this 2x2 frequency domain unit is as described the second nature type, wherein, THD3 is the 3rd threshold value, THD4 is the 4th threshold value;

Wherein, F element is the upper right corner value of described 2x2 frequency domain unit, and G element is the lower left corner value of described 2x2 frequency domain unit.

37. image compressing methods as claimed in claim 13, is characterized in that: between described step (E) and step (F), also comprise step:

Described 2x2 frequency domain unit is divided into the first natural type, the second nature type or Third Nature type by (H '), wherein,

When the H element of the first colourity 2x2 frequency domain unit (U) meets following formula,

H＞THD1

Judge that described 2x2 coding unit is as the first natural type;

When F element and G element in the first colourity 2x2 frequency domain unit (U) meet following formula,

MAX(ABS(F,0),ABS(G,0))≤THD2

And F element and G element in the second colourity 2x2 frequency domain unit (V) meet following formula,

MAX(ABS(F,0),ABS(G,0))≤THD3

Judge that described 2x2 coding unit is as the second nature type;

Do not meet the first natural type and the second nature type condition, judge that described 2x2 coding unit is as Third Nature type;

Wherein, THD1 is the first threshold value, and THD2 is the second threshold value, THD3 is the 3rd threshold value, F element is the upper right corner value of described 2x2 frequency domain unit, and G element is the lower left corner value of described 2x2 frequency domain unit, and H element is the lower right corner value of described 2x2 frequency domain unit.

38. image compressing methods as claimed in claim 5, is characterized in that: in step (C), in the time that described 2x2 coding unit is the first artificial type, the second artificial type or the 3rd artificial type, use the wherein mean value of two pixels of 8 records; Use 7 record one 7 bit table cases to put, the content that records that described 7 bit table cases are put is: all record in content in these 7 bit table lattice, differs reckling with the difference of the mean value of other two pixels in this 2x2 coding unit and the mean value of aforesaid two pixels.

39. image compressing methods as claimed in claim 5, it is characterized in that: in step (C), when 2x2 coding unit is that the 4th artificial type, the 5th artificial type, Sixth Man are while making type or the 7th artificial type, use the wherein mean value of three pixels of 8 records, use 7 or 6 quantized values that record another one pixel in this 2x2 coding unit.

40. image compressing methods as claimed in claim 5, is characterized in that: in step (F), in the time that described 2x2 frequency domain unit is the first natural type, use 7 E element, F element and G elements that record in described lightness 2x2 frequency domain unit; Use 4 record one 4 bit table cases to put, the content that records that described 4 bit table cases are put is: all of these 4 bit table lattice record in content, with the reckling in the difference of the value of the H element in this lightness 2x2 frequency domain unit; Wherein, E element is the upper left corner value of described 2x2 frequency domain unit, and F element is the upper right corner value of described 2x2 frequency domain unit, and G element is the lower left corner value of described 2x2 frequency domain unit, and H element is the lower right corner value of described 2x2 frequency domain unit.

41. image compressing methods as claimed in claim 5, is characterized in that: in step (F), in the time that described 2x2 frequency domain unit is the first natural type, use 7 E elements that record in described the first colourity 2x2 frequency domain unit; Use 2 record one 2 bit table cases to put, the content that records that this 2 bit table case is put is: all of these 2 bit table lattice record in content, with the reckling in the difference of the mean value of F element in this first colourity 2x2 frequency domain unit and G element; Do not record the H element in this first colourity 2x2 frequency domain unit; Wherein, E element is the upper left corner value of described 2x2 frequency domain unit, and F element is the upper right corner value of described 2x2 frequency domain unit, and G element is the lower left corner value of described 2x2 frequency domain unit, and H element is the lower right corner value of described 2x2 frequency domain unit.

42. image compressing methods as claimed in claim 5, is characterized in that: in step (F), in the time that described 2x2 frequency domain unit is the first natural type, use 7 E elements that record in described the second colourity 2x2 frequency domain unit; Use 2 record one 2 bit table cases to put, the content that records that this 2 bit table case is put is: all of these 2 bit table lattice record in content, with the reckling in the difference of the mean value of F element in this second colourity 2x2 frequency domain unit and G element; Use 3 record one 3 bit table cases to put, the content that records that this 3 bit table case is put is: all of these 3 bit table lattice record in content, with the reckling in the difference of the H element of this second colourity 2x2 frequency domain unit; Wherein, E element is the upper left corner value of described 2x2 frequency domain unit, and F element is the upper right corner value of described 2x2 frequency domain unit, and G element is the lower left corner value of described 2x2 frequency domain unit, and H element is the lower right corner value of described 2x2 frequency domain unit.

43. image compressing methods as claimed in claim 5, is characterized in that: in step (F), in the time that described 2x2 frequency domain unit is the second nature type, use 6 quantized values that record the E element in described lightness 2x2 frequency domain unit; Use 5 quantized values that record the F element of described lightness 2x2 frequency domain unit; Use 5 quantized values that record the G element of described lightness 2x2 frequency domain unit; Use 3 record one 3 bit table cases to put, the content that records that this 3 bit table case is put is: all of these 3 bit table lattice record in content, with the reckling in the difference of the H element of this lightness 2x2 frequency domain unit; Wherein, E element is the upper left corner value of described 2x2 frequency domain unit, and F element is the upper right corner value of described 2x2 frequency domain unit, and G element is the lower left corner value of described 2x2 frequency domain unit, and H element is the lower right corner value of described 2x2 frequency domain unit.

44. image compressing methods as claimed in claim 5, is characterized in that: in step (F), in the time that described 2x2 frequency domain unit is the second nature type, use 5 quantized values that record the E element in described the first colourity 2x2 frequency domain unit; Use 3 record one 3 bit table cases to put, the content that records that this 3 bit table case is put is: all of these 3 bit table lattice record in content, with the reckling in the difference of the F element in this first colourity 2x2 frequency domain unit; Use 3 record one 3 bit table cases to put, the content that records that this 3 bit table case is put is: all of these 3 bit table lattice record in content, with the reckling in the difference of the G element in this first colourity 2x2 frequency domain unit; Do not record the H element of this first colourity 2x2 frequency domain unit; Wherein, E element is the upper left corner value of described 2x2 frequency domain unit, and F element is the upper right corner value of described 2x2 frequency domain unit, and G element is the lower left corner value of described 2x2 frequency domain unit, and H element is the lower right corner value of described 2x2 frequency domain unit.

45. image compressing methods as claimed in claim 5, is characterized in that: in step (F), in the time that described 2x2 frequency domain unit is the second nature type, use 5 quantized values that record the E element in described the second colourity 2x2 frequency domain unit; Use 4 record one 4 bit table cases to put, the content that records that this 4 bit table case is put is: all of these 4 bit table lattice record in content, with the reckling in the difference of the F element in this second colourity 2x2 frequency domain unit; Use 4 record one 4 bit table cases to put, the content that records that this 4 bit table case is put is: all of these 4 bit table lattice record in content, with the reckling in the difference of the G element in this second colourity 2x2 frequency domain unit; Use 3 record one 3 bit table cases to put, the content that records that this 3 bit table case is put is: all of these 3 bit table lattice record in content, with the reckling in the difference of the H element in this second colourity 2x2 frequency domain unit; Wherein, E element is the upper left corner value of described 2x2 frequency domain unit, and F element is the upper right corner value of described 2x2 frequency domain unit, and G element is the lower left corner value of described 2x2 frequency domain unit, and H element is the lower right corner value of described 2x2 frequency domain unit.

46. image compressing methods as claimed in claim 13, it is characterized in that: in step (C), when described 2x2 coding unit is the first artificial type, when the second artificial type and the 3rd artificial type, use the wherein mean value of two pixels of 8 records, use one 6 of 6 or 7 records or 7 bit table cases to put, the content that records that these 6 or 7 bit table cases are put is: these 6 or all of 7 bit table lattice record in content, the difference of the mean value of two pixels that record with mean value and 8 of the aforesaid uses of other two pixels in this 2x2 coding unit differs reckling.

47. image compressing methods as claimed in claim 13, it is characterized in that: in step (C), in the time that described 2x2 coding unit is the 4th artificial type to the seven artificial type, use the wherein mean value of three pixels of 8 records, use 7 or 6 quantized values that record another one pixel in described 2x2 coding unit.

48. image compressing methods as claimed in claim 13, it is characterized in that: in step (C), in the time that described 2x2 coding unit is the 8th artificial type to the 13 artificial type, use the wherein quantized value of two pixel average of 5 records, use 4 quantized values that record respectively all the other two pixels; Or use the wherein quantized value of two pixel average of 7 records, use 5 quantized values that record all the other two pixels.

49. image compressing methods as claimed in claim 13, is characterized in that: in step (C), in the time that described 2x2 coding unit is the 14 artificial type to the 17 artificial type, uses 8 pixel data is carried out to complete record.

50. image compressing methods as claimed in claim 37, it is characterized in that: in step (F), in the time that described 2x2 frequency domain unit is the first natural type, use the quantized value of 5 E elements that record lightness 2x2 frequency domain unit, F element, G element; Use 3 record one 3 bit table cases to put, the content that records that this 3 bit table case is put is: all of these 3 bit table lattice record in content, with the difference reckling of the value of the H element of described lightness 2x2 frequency domain unit; Wherein, E element is the upper left corner value of described 2x2 frequency domain unit.

51. image compressing methods as claimed in claim 37, is characterized in that: in step (F), in the time that described 2x2 frequency domain unit is the first natural type, use the quantized value of the E element of 5 record the first colourity 2x2 frequency domain unit; Use 3 record one 3 bit table cases to put, the content that records that this 3 bit table case is put is: all of these 3 bit table lattice record in content, with the difference reckling of the value of the F element of described the first colourity 2x2 frequency domain unit; Use 3 record one 3 bit table cases to put, the content that records that this 3 bit table case is put is: all of these 3 bit table lattice record in content, with the difference reckling of the value of the G element of described the first colourity 2x2 frequency domain unit; Use 3 record one 3 bit table cases to put, the content that records that this 3 bit table case is put is: all of these 3 bit table lattice record in content, with the difference reckling of the value of the H element of described the first colourity 2x2 frequency domain unit 770; Wherein, E element is the upper left corner value of described 2x2 frequency domain unit.

52. image compressing methods as claimed in claim 37, is characterized in that: in step (F), in the time that described 2x2 frequency domain unit is the first natural type, use the quantized value of the E element of 5 record the second colourity 2x2 frequency domain unit; Use 3 record one 3 bit table cases to put, the content that records that this 3 bit table case is put is: all of these 3 bit table lattice record in content, with the difference reckling of the value of the F element of described the second colourity 2x2 frequency domain unit; Use 3 record one 3 bit table cases to put, the content that records that this 3 bit table case is put is: all of these 3 bit table lattice record in content, with the difference reckling of the value of the G element of described the second colourity 2x2 frequency domain unit; Use 3 record one 3 bit table cases to put, the content that records that this 3 bit table case is put is: all of these 3 bit table lattice record in content, with the difference reckling of the value of the H element of described the second colourity 2x2 frequency domain unit; Wherein, E element is the upper left corner value of described 2x2 frequency domain unit.

53. image compressing methods as claimed in claim 37, it is characterized in that: in step (F), in the time that described 2x2 frequency domain unit is the second nature type, use the quantized value of 7 E elements that record lightness 2x2 frequency domain unit, F element, G element; Use 4 record one 4 bit table cases to put, the content that records that this 4 bit table case is put is: all of these 4 bit table lattice record in content, with the difference reckling of the value of the H element of described lightness 2x2 frequency domain unit; Wherein, E element is the upper left corner value of described 2x2 frequency domain unit.

54. image compressing methods as claimed in claim 37, is characterized in that: in step (F), in the time that described 2x2 frequency domain unit is the second nature type, use the quantized value of the E element of 6 record the first colourity 2x2 frequency domain unit; Use 2 record one 2 bit table cases to put, the content that records that this 2 bit table case is put is: all of these 2 bit table lattice record in content, with the reckling in the difference of the described first F element of colourity 2x2 frequency domain unit and the mean value of G element; Do not record the H element of described the first colourity 2x2 frequency domain unit; Wherein, E element is the upper left corner value of described 2x2 frequency domain unit.

55. image compressing methods as claimed in claim 37, is characterized in that: in step (F), in the time that described 2x2 frequency domain unit is the second nature type, use the quantized value of the E element of 7 record the second colourity 2x2 frequency domain unit; Use 2 record one 2 bit table cases to put, the content that records that this 2 bit table case is put is: all of these 2 bit table lattice record in content, with the reckling in the difference of the mean value of F element in described the second colourity 2x2 frequency domain unit and G element; Use 3 record one 3 bit table cases to put, the content that records that this 3 bit table case is put is: all of these 3 bit table lattice record in content, with the reckling in the difference of the value of the H element of described the second colourity 2x2 frequency domain unit; Wherein, E element is the upper left corner value of described 2x2 frequency domain unit.

56. image compressing methods as claimed in claim 37, is characterized in that: in step (F), in the time that described 2x2 frequency domain unit is Third Nature type, use 5 quantized values that record the E element of lightness 2x2 frequency domain unit; Use 3 record one 3 bit table cases to put, the content that records that this 3 bit table case is put is: all of these 3 bit table lattice record in content, with the reckling in the difference of the value of the F element of described lightness 2x2 frequency domain unit; Use 3 record one 3 bit table cases to put, the content that records that this 3 bit table case is put is: all of these 3 bit table lattice record in content, with the reckling in the difference of the value of the G element of described lightness 2x2 frequency domain unit; Use 2 record one 2 bit table cases to put, the content that records that this 2 bit table case is put is: all of these 2 bit table lattice record in content, with the reckling in the difference of the value of the H element of described lightness 2x2 frequency domain unit; Wherein, E element is the upper left corner value of described 2x2 frequency domain unit.

57. image compressing methods as claimed in claim 37, is characterized in that: in step (F), in the time that described 2x2 frequency domain unit is Third Nature type, use the quantized value of the E element of 4 record the first colourity 2x2 frequency domain unit; Use 4 record one 4 bit table cases to put, the content that records that this 4 bit table case is put is: all of these 4 bit table lattice record in content, with the reckling in the difference of the value of the F element of described the first colourity 2x2 frequency domain unit; Use 4 record one 4 bit table cases to put, the content that records that this 4 bit table case is put is: all of these 4 bit table lattice record in content, with the reckling in the difference of the value of the G element of described the first colourity 2x2 frequency domain unit; Use 4 record one 4 bit table cases to put, the content that records that this 4 bit table case is put is: all of these 4 bit table lattice record in content, with the reckling in the difference of the value of the H element of described the first colourity 2x2 frequency domain unit; Wherein, E element is the upper left corner value of described 2x2 frequency domain unit.

58. image compressing methods as claimed in claim 37, is characterized in that: in step (F), in the time that described 2x2 frequency domain unit is Third Nature type, use the quantized value of the E element of 4 record the second colourity 2x2 frequency domain unit; Use 4 record one 4 bit table cases to put, the content that records that this 4 bit table case is put is: all of these 4 bit table lattice record in content, with the reckling in the difference of the value of the F element of described the second colourity 2x2 frequency domain unit; Use 4 record one 4 bit table cases to put, the content that records that this 4 bit table case is put is: all of these 4 bit table lattice record in content, with the reckling in the difference of the value of the G element of described the second colourity 2x2 frequency domain unit; Use 4 record one 4 bit table cases to put, the content that records that this 4 bit table case is put is: all of these 4 bit table lattice record in content, with the reckling in the difference of the value of the H element of described the second colourity 2x2 frequency domain unit; Wherein, E element is the upper left corner value of described 2x2 frequency domain unit.

59. image compressing methods as claimed in claim 5, is characterized in that: described 2x2 coding unit is 96, and the coding package of described 2x2 coding unit is 48.

60. image compressing methods as claimed in claim 14, it is characterized in that: in step (C), in the time that described 2x2 coding unit is the first artificial type, the second artificial type or the 3rd artificial type, use the wherein mean value of two pixels of 6 records; Use one 5 of 5 or 4 records or 4 bit table cases to put, the content that records that described 5 or 4 bit table cases are put is: all record in content in these 5 or 4 bit table lattice, differs reckling with the difference of the mean value of other two pixels in this 2x2 coding unit and the mean value of aforesaid two pixels.

61. image compressing methods as claimed in claim 14, it is characterized in that: in step (C), when 2x2 coding unit is that the 4th artificial type, the 5th artificial type, Sixth Man are while making type or the 7th artificial type, use the wherein mean value of three pixels of 6 records, use 5 or 4 quantized values that record another one pixel in this 2x2 coding unit.

62. image compressing methods as claimed in claim 14, it is characterized in that: in step (C), in the time that 2x2 coding unit is the 8th artificial type to the 13 artificial type, use 5 or the wherein quantized value of two close pixel average of 4 records, use respectively 3 quantized values that record another two pixels.

63. image compressing methods as claimed in claim 14, is characterized in that: in step (C), in the time that 2x2 coding unit is the 14 artificial type to the 17 artificial type, uses 6 pixel data is carried out to complete record.

64. image compressing methods as claimed in claim 14, it is characterized in that: in step (F), in the time that described 2x2 frequency domain unit is the first natural type, use 5 quantized values that record E element, F element and G element in described lightness 2x2 frequency domain unit; Use 3 record one 3 bit table cases to put, the content that records that described 3 bit table cases are put is: all of these 3 bit table lattice record in content, with the reckling in the difference of the value of the H element in this lightness 2x2 frequency domain unit; Wherein, E element is the upper left corner value of described 2x2 frequency domain unit, and F element is the upper right corner value of described 2x2 frequency domain unit, and G element is the lower left corner value of described 2x2 frequency domain unit, and H element is the lower right corner value of described 2x2 frequency domain unit.

65. image compressing methods as claimed in claim 14, is characterized in that: in step (F), in the time that described 2x2 frequency domain unit is the first natural type, use 5 quantized values that record the E element in described the first colourity 2x2 frequency domain unit; Use 2 record one 2 bit table cases to put, the content that records that this 2 bit table case is put is: all of these 2 bit table lattice record in content, with the reckling in the difference of the mean value of F element in this first colourity 2x2 frequency domain unit and G element; Do not record the H element in this first colourity 2x2 frequency domain unit; Wherein, E element is the upper left corner value of described 2x2 frequency domain unit, and F element is the upper right corner value of described 2x2 frequency domain unit, and G element is the lower left corner value of described 2x2 frequency domain unit, and H element is the lower right corner value of described 2x2 frequency domain unit.

66. image compressing methods as claimed in claim 14, is characterized in that: in step (F), in the time that described 2x2 frequency domain unit is the first natural type, use 5 quantized values that record the E element in described the second colourity 2x2 frequency domain unit; Use 2 record one 2 bit table cases to put, the content that records that this 2 bit table case is put is: all of these 2 bit table lattice record in content, with the reckling in the difference of the mean value of F element in this second colourity 2x2 frequency domain unit and G element; Use 2 record one 2 bit table cases to put, the content that records that this 2 bit table case is put is: all of these 2 bit table lattice record in content, with the reckling in the difference of the H element of this second colourity 2x2 frequency domain unit; Wherein, E element is the upper left corner value of described 2x2 frequency domain unit, and F element is the upper right corner value of described 2x2 frequency domain unit, and G element is the lower left corner value of described 2x2 frequency domain unit, and H element is the lower right corner value of described 2x2 frequency domain unit.

67. image compressing methods as claimed in claim 14, is characterized in that: in step (F), in the time that described 2x2 frequency domain unit is the second nature type, use 4 quantized values that record the E element in described lightness 2x2 frequency domain unit; Use 3 record one 3 bit table cases to put, the content that records that this 3 bit table case is put is: all of these 3 bit table lattice record in content, with the reckling in the difference of the F element of this lightness 2x2 frequency domain unit; Use 3 record one 3 bit table cases to put, the content that records that this 3 bit table case is put is: all of these 3 bit table lattice record in content, with the reckling in the difference of the G element of this lightness 2x2 frequency domain unit; Use 2 record one 2 bit table cases to put, the content that records that this 2 bit table case is put is: all of these 2 bit table lattice record in content, with the reckling in the difference of the H element of this lightness 2x2 frequency domain unit; Wherein, E element is the upper left corner value of described 2x2 frequency domain unit, and F element is the upper right corner value of described 2x2 frequency domain unit, and G element is the lower left corner value of described 2x2 frequency domain unit, and H element is the lower right corner value of described 2x2 frequency domain unit.

68. image compressing methods as claimed in claim 14, is characterized in that: in step (F), in the time that described 2x2 frequency domain unit is the second nature type, use 3 quantized values that record the E element in described the first colourity 2x2 frequency domain unit; Use 3 record one 3 bit table cases to put, the content that records that this 3 bit table case is put is: all of these 3 bit table lattice record in content, with the reckling in the difference of the F element in this first colourity 2x2 frequency domain unit; Use 3 record one 3 bit table cases to put, the content that records that this 3 bit table case is put is: all of these 3 bit table lattice record in content, with the reckling in the difference of the G element in this first colourity 2x2 frequency domain unit; Use 2 record one 2 bit table cases to put, the content that records that this 2 bit table case is put is: all of these 2 bit table lattice record in content, with the reckling in the difference of the H element of this lightness 2x2 frequency domain unit; Wherein, E element is the upper left corner value of described 2x2 frequency domain unit, and F element is the upper right corner value of described 2x2 frequency domain unit, and G element is the lower left corner value of described 2x2 frequency domain unit, and H element is the lower right corner value of described 2x2 frequency domain unit.

69. image compressing methods as claimed in claim 14, is characterized in that: in step (F), in the time that described 2x2 frequency domain unit is the second nature type, use 3 quantized values that record the E element in described the first colourity 2x2 frequency domain unit; Use 3 record one 3 bit table cases to put, the content that records that this 3 bit table case is put is: all of these 3 bit table lattice record in content, with the reckling in the difference of the F element in this first colourity 2x2 frequency domain unit; Use 3 record one 3 bit table cases to put, the content that records that this 3 bit table case is put is: all of these 3 bit table lattice record in content, with the reckling in the difference of the G element in this first colourity 2x2 frequency domain unit; Use 2 record one 2 bit table cases to put, the content that records that this 2 bit table case is put is: all of these 2 bit table lattice record in content, with the reckling in the difference of the H element of this lightness 2x2 frequency domain unit; Wherein, E element is the upper left corner value of described 2x2 frequency domain unit, and F element is the upper right corner value of described 2x2 frequency domain unit, and G element is the lower left corner value of described 2x2 frequency domain unit, and H element is the lower right corner value of described 2x2 frequency domain unit.

70. image compressing methods as claimed in claim 14, is characterized in that: described 2x2 coding unit is 72, and the coding package of described 2x2 coding unit is 36.

The 71. 1 kinds of image compression with fixing compression ratio, decompression systems based on 2x2 coding unit, is characterized in that, described system comprises:

One display module, for showing described image;

One image input equipment, for inputting described image;

One fixing compression ratio image compression device based on 2x2 coding unit, is connected to described image input equipment, for this image is encoded, to generate coding package;

One apparatus for temporary storage, is connected to the described fixing compression ratio image compression device based on 2x2 coding unit, for described coding package;

One fixing compression ratio image decompressing device based on 2x2 coding unit, is connected to described apparatus for temporary storage, for receiving described coding package, and this coding package is decompressed, to produce the 2x2 decoding unit corresponding with described 2x2 coding unit; And

Time schedule controller, is connected to the described fixing compression ratio image decompressing device based on 2x2 coding unit, and for receiving described 2x2 decoding unit, the sequential that produces described display module drives signal and shows data,

Wherein, described fixing compression ratio image compression device first judges that described 2x2 coding unit is artificial type or natural type, with the coding that carries out differential errors coding, quantizes and table look-up of the 2x2 coding unit to this artificial type, and then generation first coding data, and to the 2x2 coding unit of this natural type coding that carries out color gamut conversion, discrete cosine transform, quantizes and table look-up, and then generation the second coded data, again this first coding data or this second coded data are encapsulated, to produce the coding package with fixing compression ratio;

Wherein, described artificial type comprises the first to the 7th artificial type; Wherein the first artificial type list shows wherein four pixels, two horizontal stripes in horizontal direction, and top left corner pixel and upper right corner pixel are approximate, and lower left corner pixel and lower right corner pixel approximate; The second artificial type represents that wherein four pixels are two vertical stripes of vertical direction, and top left corner pixel and lower left corner pixel are approximate, and upper right corner pixel and lower right corner pixel approximate; The 3rd artificial type represents that wherein the two slanted bar lines that four pixels are miter angle direction intersect, and top left corner pixel and lower right corner pixel are approximate, and lower left corner pixel and upper right corner pixel approximate; The the 4th to the 7th artificial type represents wherein the combination with single-point triangular in shape of four pixels; I.e. the 4th artificial type, represents that lower left corner pixel, upper right corner pixel and lower right corner pixel are approximate; The 5th artificial type, represents that top left corner pixel, upper right corner pixel and lower right corner pixel are approximate; Sixth Man is made type, represents that top left corner pixel, lower left corner pixel and upper right corner pixel are approximate; The 7th artificial type, represents that top left corner pixel, lower left corner pixel and lower right corner pixel are approximate.

72. 1 kinds of image decompression methods with fixing compression ratio based on 2x2 coding unit, it is characterized in that: a coding package is decoded, with the 2x2 decoding unit in reconstructed image, described 2x2 decoding unit comprises four pixels that are matrix arrangement, at least one 2x2 decoding unit forms described image, and described image decompression method comprises the following steps:

(A) receive described coding package;

(B) judge according to the main packet header of this coding package whether this coding package is artificial type, if so, judge that this coding package is behaved to make the coding package of type, otherwise, judge the coding package that this coding package is natural type;

(C) the coding package of this artificial type is carried out to inverse quantization, counter table look-up decoding and contrast point error decoding, to produce the first decoded data;

(D) the coding package of this natural type is carried out to inverse quantization and the anti-decoding of tabling look-up, to produce the second decoded data;

(E) this second decoded data is carried out to discrete cosine transform, to produce the 3rd decoded data;

(F) the 3rd decoded data is carried out to color gamut conversion, to obtain the 4th decoded data; And

(G) receive described the first decoded data or the 4th decoded data, and the first decoded data or the 4th decoded data are rebuild, to produce 2x2 decoding unit;

Wherein, described artificial type comprises the first to the 7th artificial type; Wherein the first artificial type list shows wherein four pixels, two horizontal stripes in horizontal direction, and top left corner pixel and upper right corner pixel are approximate, and lower left corner pixel and lower right corner pixel approximate; The second artificial type represents that wherein four pixels are two vertical stripes of vertical direction, and top left corner pixel and lower left corner pixel are approximate, and upper right corner pixel and lower right corner pixel approximate; The 3rd artificial type represents that wherein the two slanted bar lines that four pixels are miter angle direction intersect, and top left corner pixel and lower right corner pixel are approximate, and lower left corner pixel and upper right corner pixel approximate; The the 4th to the 7th artificial type represents wherein the combination with single-point triangular in shape of four pixels; I.e. the 4th artificial type, represents that lower left corner pixel, upper right corner pixel and lower right corner pixel are approximate; The 5th artificial type, represents that top left corner pixel, upper right corner pixel and lower right corner pixel are approximate; Sixth Man is made type, represents that top left corner pixel, lower left corner pixel and upper right corner pixel are approximate; The 7th artificial type, represents that top left corner pixel, lower left corner pixel and lower right corner pixel are approximate.

73. image decompression methods as described in claim 72, is characterized in that, further comprising the steps of in step (B):

(H) in the time being judged to be the coding package of artificial type, judge according to the sub-packet header in described coding package whether it is in the artificial type of the first artificial type to the three, wherein, described the first artificial type is two vertical stripes that described four pixels are vertical direction, the second artificial type is two vertical stripes that described four pixels are vertical direction, and the 3rd artificial type is the two slanted bar lines intersections that described four pixels are miter angle direction; And

(I) otherwise, judge according to this sub-packet header of this coding package and second son packet header whether it is in the artificial type of the 4th artificial type to the seven again, wherein, the artificial type of described the 4th artificial type to the seven is the combinations with single-point triangular in shape of described four pixels.

74. image decompression methods as described in claim 72, is characterized in that: between step (C) and step (D), further comprising the steps of:

(J) for the coding package of described natural type, judge that according to the sub-packet header of this coding package it is the first natural type or the second nature type.

75. image decompression methods as described in claim 74, is characterized in that: in step (E), the transition matrix coefficient of described discrete cosine transform is:

$\left[\begin{array}{c}\stackrel{\&OverBar;}{A}\\ \stackrel{\&OverBar;}{B}\\ \stackrel{\&OverBar;}{C}\\ \stackrel{\&OverBar;}{D}\end{array}\right]=\left[\begin{array}{cccc}1& 1& 1& 1\\ 1& -1& 1& -1\\ 1& 1& -1& -1\\ 1& -1& -1& 1\end{array}\right]\left[\begin{array}{c}E\\ F\\ G\\ H\end{array}\right],$

Wherein, E, F, G, H are described the second decoded data, for described the 3rd decoded data.

76. image decompression methods as described in claim 75, is characterized in that: in step (F), carry out YUV to RGB color gamut conversion, the transition matrix coefficient of described YUV to RGB color gamut conversion is:

$\left[\begin{array}{c}r\\ g\\ b\end{array}\right]=\left[\begin{array}{ccc}1.0& -0.5& -0.5\\ 1.0& 0.5& 0\\ 1.0& -0.5& 0.5\end{array}\right]\left[\begin{array}{c}Y\\ U\\ V\end{array}\right],$

Wherein, Y is the lightness of the pixel in described the 3rd decoded data, the colourity that U and V are this pixel; R is the red value of the pixel in the 4th decoded data, the green value that g is this pixel, the blue valve that b is this pixel.