JP4771541B2 - Image encoding apparatus and method, computer program, and computer-readable storage medium - Google Patents

Description

  The present invention relates to an image data encoding technique.

  As one of the image encoding techniques, in the process of scanning an image in the raster scan order, the predicted value of the target pixel is obtained using its surrounding pixels, and the difference value between the predicted value and the actual value of the target pixel is encoded. There is a predictive coding method. Conventionally, in such a predictive encoding method, the state of the target pixel is classified based on the encoded pixels, and the compression performance is improved by encoding according to the probability distribution of the prediction error in each state. Is generally done. For example, JPEG-LS Part 1 (Non-Patent Document 1) recommended by ISO and ITU-T as an international standard system for reversible and quasi-reversible compression of continuous tone still images refers to four pixels surrounding the target pixel. The difference between pixels is obtained. Then, based on these differences, the prediction error is encoded by separating into 365 states.

  Hereinafter, a state generation method in JPEG-LS will be described. In the following description, matters not directly related to the present invention are omitted, for example, assuming that the parameter NEAR representing the allowable range of error for quasi-reversible encoding is 0. Please refer.

FIG. 3 shows the relative positional relationship between surrounding pixels (a, b, c, d) referred to in JPEG-LS and the target pixel x. Since the pixels are encoded in the raster scan order, the illustrated pixels a, b, c, and d are all encoded. First, the differences between a and c, c and b, and b and d are obtained by the following equations, and are set as D1, D2, and D3, respectively.
D1 = db
D2 = b−c
D3 = c−a

The difference values D1, D2, and D3 are quantized in nine ways (from -4 to 4) to obtain quantized values Q1, Q2, and Q3 of the respective differences. FIG. 2 shows the correspondence between the range of the difference value and its quantized value. T1, T2, T3 are predetermined non-negative integer values. For example, values of T1 = 3, T2 = 7, T3 = 21 are set for an 8-bit image that takes a value of 0 to 255. The combination {Q, Q2, Q3} of Q1, Q2, and Q3 obtained in this way has nine values from -4 to 4, respectively, so that 9 × 9 × 9 = 729 ways. Since the probability that the prediction error e occurs in the states {Q1, Q2, Q3} can be considered to be the same as the probability that the prediction error -e occurs in the states {−Q1, −Q2, −Q3}, these states are integrated. Degenerate to 365 ways. A prediction error is encoded in accordance with the probability distribution assumed in the 365 states. JPEG-LS holds the sum of the absolute values of prediction errors and the number of occurrences of each state for each state, and sets a Golomb encoding parameter k from these values, thereby adapting to the probability distribution of each state. To do. Initial values are set for these values at the start of encoding, and the values are updated as needed during the encoding process, so that the probability distribution of each state is dynamically followed.
ITU-T T.87 (1998) | ISO / IEC 14495-1: 1999, Information Technology-Lossless and near-lossless compression of continuous-tone still images: Baseline

In the state-dependent predictive coding described above, when coding is performed by separating the n states from S1 to Sn, the prediction error e is determined based on the appearance probability P (e | Si) in each state. The entropy H (n) is given by the following equation.
H (n) = −ΣP (e | Si) log ₂ P (e | Si)
(Where Σ is the sum of i = 1 to n)

  Since there is a relationship of H (n) ≧ H (n + 1), an improvement in compression performance is expected by increasing the number of states. However, in the above-described one-pass image encoding scheme such as JPEG-LS, the probability model is updated so as to follow the probability distribution of each state while encoding. For this reason, if the number of states is increased too much, the number of occurrences of each state decreases, and the encoding ends without sufficient adaptation of the probability distribution. That is, the compression performance is reduced. Similarly, when a small image such as 32 × 32 is encoded, there is a problem that sufficient probability tracking is not performed with the number of states of 365.

  The present invention has been made in view of the above-mentioned problems. In one aspect of the present invention, when small-size image data is subjected to state-dependent predictive coding, or when an image is divided into blocks and state-dependent predictive coding is performed independently, It is an object of the present invention to provide a technique for improving compression performance by setting an appropriate number of states for each size or block size and encoding.

In order to solve this problem, for example, an image encoding device of the present invention has the following configuration. That is,
In the encoded pixel group around the pixel of interest, the difference between the fixed number of pixel pairs is calculated in advance, and the difference value of each calculated pixel pair is quantized. Classifying the surrounding state of the pixel of interest on the basis of, and encoding the pixel of interest according to a probability model corresponding to the classified state,
Quantization parameter setting means for setting a quantization parameter for performing the quantization according to size information indicating a size of an image to be encoded;
Difference calculation means for calculating a difference value of a fixed number of pixel pairs that are in a preset positional relationship in the encoded pixel group around the pixel of interest;
Quantization means for quantizing a difference value of each pixel pair calculated by the difference calculation means according to a quantization parameter set by the quantization parameter setting means;
State determining means for determining the state around the pixel of interest based on the quantized value of each pixel pair obtained by the quantizing means;
An encoding unit that encodes the pixel of interest using the state determined by the state determination unit as an encoding parameter ;
The quantization parameter setting means sets a quantization parameter for reducing the number of values that can be taken after the quantization by the quantization means as the size of the image to be encoded is smaller. .

  According to the configuration of the present invention, it is possible to perform efficient encoding even in a small-size image or a small-size tile unit image. In addition, in order to improve random accessibility and parallel processability, even when divided into blocks and independently predictively encoded, higher-efficiency encoding is possible.

  Hereinafter, embodiments according to the present invention will be described in detail with reference to the accompanying drawings.

<First Embodiment>
FIG. 1 is a block diagram of an image processing apparatus (or image encoding apparatus) according to this embodiment.

  As illustrated in FIG. 1, the apparatus according to the present embodiment includes an image input unit 101, a line buffer 102, a lossless encoding unit 103, a code string forming unit 104, and a state number determining unit 105. In the figure, reference numerals 106, 107 and 108 denote signal lines. The generation source of the image data input by the image input unit 101 is an image scanner, but the type of storage medium that stores the image data, a server on the network, or the like is not limited.

  Hereinafter, the processing of the image processing apparatus of the present embodiment will be described with reference to FIG.

  First, as a premise, the encoding target image in the image processing apparatus according to the present embodiment is RGB color image data, and each component (color) is expressed by a luminance value of 8 bits (range 0 to 255). And The image data to be encoded is arranged in dot order, that is, in the raster scan order, and the pixels are arranged in the order of R, G, and B. The size of the image is assumed to be the number of horizontal pixels W and the number of vertical pixels H. The color image is not limited to RGB, but may be YCbCr or another color space. Each component is not limited to 8 bits. It should be recognized that the above is merely an example.

  Next, the operation of each unit in the image processing apparatus of this embodiment will be described.

  First, prior to inputting the encoding target image data, the horizontal pixel number W and the vertical pixel number H of the image to be encoded are input from the signal line 106 and the signal line 107, respectively. These are uniquely determined by the size of the original and the reading resolution of the image scanner. In addition, when image data stored in a storage medium is to be encoded, it can be obtained by analyzing information included in the header of the file.

  Subsequently, encoding target image data is input from the image input unit 101 in the order of raster scanning.

  The line buffer 102 has an area for storing image data for two lines, and sequentially stores image data input from the image input unit 101. The capacity required for the line buffer 102 is W × 2 × 3 (for RGB) bytes.

  The lossless encoding unit 103 refers to the newly stored image data of one line of the image data of two lines stored in the line buffer 102, and the image data of the immediately previous line stored before that. Then, encoding is performed according to the encoding algorithm defined as the JPEG-LS Baseline line interleave mode, and the encoded data is output to the code string forming unit 104. At this time, the threshold values T1, T2, and T3 used for state separation use values given from the state number determination unit 105 described later. The details of the encoding by the line interleave mode of JPEG-LS Baseline are described in detail in the recommendation, and thus the description thereof is omitted here.

  The state number determination unit 105 determines threshold numbers T1 and T2 for determining the number of states in predictive encoding in the lossless encoding unit 103 based on the horizontal and vertical pixel numbers W and H input from the signal line 106 and the signal line 107. T3 is determined. Specific examples are shown below.

  First, the state number determination unit 105 obtains the product of W and H, and obtains the total number of pixels R of the image data to be encoded. This R is compared with threshold values Th1 and Th2 for determining the number of pixels, and the number of states is determined from the magnitude relationship.

  If R <Th1, T1 = T2 = T3 = 1 so that 14 states are obtained. With this setting, in the state separation performed by the lossless encoding unit 103, if the difference value of the surrounding pixels is −1 or less, the quantization value is −4, 0 is 0, and 4 is 1 or more. The difference quantization values are -4, 0, and 4.

  If Th1 ≦ R <Th2, T1 = T2 = T3 = 7 so that the state becomes 63. In this case, the quantized value of the difference value is -4, -1, 0, 1, 4 in five ways.

  The threshold values T1 = 3, T2 = 7, and T3 = 21 are set so that the 365 state is obtained when Th2 ≦ R. In this case, all nine patterns of -4, -3, -2, -1, 0, 1, 2, 3, 4 can occur as the quantized values of the difference values.

  Here, the threshold values Th1 and Th2 for determining the number of pixels are set to values such as Th1 = 1024 and Th2 = 4096, for example. Therefore, in this case, in an image having the same number of pixels in the horizontal and vertical directions, the number of states is 14 in an image smaller than 32 × 32. Also, if the image to be encoded is 32 × 32 or larger and less than 64 × 64, it is switched to 63, and if it is 64 × 64 or larger, 365 is switched.

  The code string forming unit 104 adds necessary additional information to the encoded data output from the lossless encoding unit 103 to form a code string serving as an output of the image processing apparatus and outputs the code string from the signal line 108. FIG. 7 is a diagram showing a configuration of an output code string of the image processing apparatus. At the head of the output code string, information necessary for decoding an image, for example, additional information such as the number of pixels in the horizontal direction, the number of pixels in the vertical direction, the number of components, and the number of bits of each component is JPEG-LS standard. It is attached as a header in a format compliant with. The header portion also includes an LSE marker segment including the values of T1, T2, and T3 output from the state number determination unit 105.

  FIG. 4 is a flowchart showing the flow of the encoding process of the encoding target image data in the image processing apparatus according to this embodiment. The overall flow of the image encoding process performed by the image processing apparatus according to this embodiment will be described below with reference to the flowchart shown in FIG.

  First, the number of pixels W in the horizontal direction and the number of pixels H in the vertical direction of the encoding target image are input from the signal line 106 and the signal line 107, and threshold values T1, T2, and T3 for determining the number of states are determined by the state number determination unit 105. (Step S400).

  Next, the code string forming unit 104 uses the JPEG-LS standard based on T1, T2, and T3 output from the state number determining unit 105, the horizontal pixel number W, the vertical pixel number H, and the like of the encoding target image. Are generated (step S401).

  Next, the image input unit 101 starts input of image data, and stores data for one line of image data to be encoded in the line buffer 102 (step S402). It is assumed that the line buffer 102 is cleared to zero before starting the encoding process of one image.

  The lossless encoding unit 103 performs lossless encoding on the line data stored in the line buffer 102, generates encoded data, and outputs the encoded data to the code string forming unit 104 (step S403).

  The code string forming unit 104 combines the encoded data output from the lossless encoding unit 105 to generate encoded data to be output from the image processing apparatus in a format defined by the JPEG-LS standard, and sequentially outputs the data to the outside of the apparatus. Is output (step S404).

  Thereafter, in step S405, it is determined whether or not the encoded line data is the last line of the encoding target image. If the encoded line data is not the last line (NO), the process returns to step S402 to return to the next line. The data is read and processing continues. On the other hand, if it is the last line (YES), the encoding process for the target image data is terminated. With the above processing, the entire image is encoded.

  Since the encoded data generated by the image processing apparatus of this embodiment is in the format of encoded data defined by the JPEG-LS standard, it can be decoded by a decoding apparatus compliant with the JPEG-LS standard.

  As described above, in the image processing device according to the present embodiment, the number of states is switched according to the size of the image, so that it is easy to adapt to the established distribution of each state, and the efficiency of predictive coding is increased. Can be improved.

  The relationship between the image size (horizontal and vertical pixel count) and the threshold values Th1 and Th2 is merely an example, and the present invention is not limited to the above embodiment.

<Modification of First Embodiment>
In the above embodiment, the image data is encoded with the apparatus configuration shown in FIG. 1, but a process equivalent to the above is performed by software (application program) of a general-purpose information processing apparatus such as a personal computer. Is also possible.

  FIG. 11 is a diagram showing a basic configuration of an information processing apparatus according to this modification.

  In the figure, reference numeral 1401 denotes a CPU that controls the entire apparatus. Reference numeral 1402 denotes a RAM used as a work area of the CPU 1401, and reference numeral 1403 denotes a ROM storing a BIOS and a boot program. Reference numeral 1404 denotes a keyboard, and 1405 denotes a mouse which is one of pointing devices. Reference numeral 1406 denotes a display control unit, which internally includes a video memory and a display controller that draws data in the video memory under the control of the CPU 1401 and outputs data stored in the video memory to the display device 1412 as a video signal. Yes. The display device 1412 is a CRT or a liquid crystal display device. Reference numeral 1407 denotes an external storage device such as a hard disk device, in which an OS (operating system) and an application program for image encoding are stored. The external storage device 1407 is also used for storing files created by various applications. A storage medium drive 1408 reads / writes data from / to a storage medium such as a flexible disk, a memory card, and a CD-ROM. Reference numeral 1409 denotes a scanner interface (USB, SCSI interface, etc.) for connecting this apparatus and the image scanner 1411. Reference numeral 1413 denotes a network interface.

  When the power of the apparatus is turned on, the CPU 1401 loads the OS from the external storage device 1407 to the RAM 1402 in accordance with the boot program stored in the ROM 1403. As a result, under the control of the OS, the GUI is drawn on the display control unit 1406, and the GUI is displayed on the display device 1412. The operator views the display on the display device 1412 and operates the keyboard 1404 and the mouse 1405. Here, when an operator gives a start instruction for an image encoding application, the CPU 1401 loads the image encoding application program in the external storage device 1407 into the RAM 1402 and executes it. As a result, this apparatus functions as an image processing apparatus.

  When the CPU 1401 executes an image encoding application and receives an input instruction for an image to be encoded from the operator, the document image is input from the image scanner 1411 and encoded. The encoding result is stored in the external storage device 1407 as a file.

  When reading a document, the size of the document is specified by GUI. Based on the size specified at that time and the resolution of the image scanner, the size of the image data to be encoded (the number of pixels in the horizontal and vertical directions) is acquired. it can. If the image scanner is provided with a sensor for detecting the document size and the detection result can be received via the scanner interface, the size of the image data to be encoded can be acquired based on the document size and the reading resolution. .

  When reading of a document is started, the CPU 1401 inputs a document image from the image scanner 1411 according to a coding application and performs coding. The encoding result is stored in the external storage device 1407 as a file.

  Here, the image encoding application has modules (also referred to as subroutines and functions) corresponding to the components shown in FIG. However, the line buffer 102 is secured in the RAM 1402 by executing the image encoding application. Therefore, it can be understood that the image encoding application basically performs the same processing as in FIG.

  Therefore, it is obvious that the present invention includes a computer program as its category. In the above description, the encoding target image is input from the image scanner 1411. However, the encoding target image data may be stored in a storage medium or downloaded from a server on the network. Applicable. Also, the output destination of the encoding result is not limited to the external storage device 1407, and may be a network, and any output destination may be used.

<Second Embodiment>
FIG. 6 is a block diagram of an image processing apparatus according to the second embodiment.

  As shown in FIG. 6, the image processing apparatus according to the present embodiment includes an image input unit 601, a line buffer 602, a block division unit 603, a tile buffer 604, a lossless encoding unit 103, a code string forming unit 605, and a state number determination. Unit 105 and tile size setting unit 606. In the figure, reference numerals 607 and 608 denote signal lines. Blocks that are the same as those in FIG. 1 described in the first embodiment are given the same numbers, and descriptions thereof are omitted.

  Hereinafter, with reference to FIG. 6, an image encoding process performed by the image processing apparatus according to the second embodiment will be described.

  The encoding target image in the image processing apparatus according to the second embodiment is a color image represented by 8-bit RGB components (colors) (brightness values in the range of 0 to 255) as in the first embodiment. It is data. The image data to be encoded is arranged in dot order, that is, in the raster scan order, and the pixels are arranged in the order of R, G, and B. The image is assumed to be composed of horizontal W pixels and vertical H pixels. The image processing apparatus according to the second embodiment divides image data into blocks and encodes each block (tile) independently. The tile size can be selected from three types of 16 × 16, 32 × 32, and 64 × 64, and is set for each encoding target image. Note that the tile size is designated by the user using the operation panel, keyboard, or the like.

  Next, the operation of each unit in the image processing apparatus of this embodiment will be described.

  First, prior to inputting the encoding target image data, a tile size selection signal for selecting a tile size is input from the signal line 607. The tile size selection signal is ternary, and “0” is input when 16 × 16 is selected, “1” is input when 32 × 32 is selected, and “2” is input when 64 × 64 is selected. Is done.

  The tile size setting unit 606 sets and outputs the horizontal pixel number Iw and the vertical pixel number Ih of the tile according to the tile size selection signal input from the signal line 607. That is, when the tile size selection signal is “0”, the tile size setting unit 606 outputs Iw = Ih = 16. When “1”, Iw = Ih = 32, and when “2”, Iw = Ih = 64 is output.

  Subsequently, the encoding target image data is input from the image input unit 601 in the raster scan order.

  The line buffer 602 has an area for storing 64 lines of image data, and sequentially stores the image data input from the image input unit 101. The capacity required for the line buffer 102, that is, the data amount of one stripe is W × 64 × 3 (for RGB) bytes. For convenience of explanation, it is assumed that the number H of vertical pixels is an integral multiple of 64.

  The block dividing unit 603 monitors the fullness of the line buffer 602 based on the tile vertical pixel count Ih output from the tile size setting unit 606, and when the image data for Ih lines is stored in the line buffer 602, The image data stored in the line buffer 602 is divided into rectangular blocks composed of horizontal Iw pixels and vertical Ih pixels, read out in units of blocks, and stored in the tile buffer 604. For convenience of explanation, it is assumed that the number of horizontal pixels W of an image is an integral multiple of Iw, and incomplete blocks do not occur when divided into rectangular blocks. Hereinafter, data obtained by dividing the encoding target image data by the width of the Ih line is referred to as a stripe, and a rectangular block composed of horizontal Iw pixels and vertical Ih pixels is referred to as a tile.

  FIG. 8 shows the relationship between image data to be encoded, stripes, and tiles. As shown in the figure, the i-th tile in the horizontal direction and the j-th tile in the vertical direction are denoted as T (i, j).

  The tile buffer 604 has an area for storing pixel data for one tile of the maximum size (64 × 64), and sequentially stores tile data output from the block dividing unit 603. The capacity required for the tile buffer 604 is 64 × 64 × 3 (for RGB) bytes.

  Similarly to the first embodiment, the lossless encoding unit 103 encodes tiles stored in the tile buffer 604 in units of lines according to an encoding algorithm defined as a JPEG-LS Baseline line interleave mode, The encoded data is output to the code string forming unit 605. At this time, the threshold values T1, T2, and T3 used for state separation use values given from the state number determination unit 105.

  The code sequence forming unit 106 combines the tile encoded data output from the lossless encoding unit 103, adds necessary additional information, forms a code sequence to be output from the image processing apparatus, and outputs the code sequence from the signal line 608. . The tile encoded data output from the lossless encoding unit 103 for each tile is an entropy encoding of the structure of JPEG-LS encoded data (see FIG. 7) obtained by encoding each tile as one image. Corresponds to the data segment part.

  FIG. 9 shows the configuration of the output code string of the image processing apparatus in the second embodiment. At the beginning of the output code string, information necessary for decoding the image, for example, the number of pixels in the horizontal direction of the image, the number of pixels in the vertical direction, attribute information indicating the color space, the number of components, the number of bits of each component, and the tile Additional information such as width and height is attached as a header. In addition, the values of T1, T2, and T3 output from the state number determination unit 105 are included in the header.

  FIG. 10 is a diagram showing the configuration of the output code string of each tile. A tile header is added to the head of each tile to include horizontal and vertical position information (i, j) of each tile. A marker is placed at the beginning or end of each tile data. Alternatively, random access in units of tiles can be made possible by managing the length of the code string of each tile by including it in the head of the tile or the header portion of the head of the encoded data.

  FIG. 5 is a flowchart showing the flow of the encoding process of the encoding target image data by the image processing apparatus according to this embodiment. The overall flow of the image encoding process performed by the image processing apparatus according to the second embodiment will be described below according to the flowchart shown in FIG.

  First, the tile size setting unit 606 receives a tile size selection signal from the signal line 607, determines the horizontal pixel number Iw and the vertical pixel number Ih of the tile according to the selection signal, and outputs it. The state number determination unit 105 determines threshold values T1, T2, and T3 for determining the number of states based on these Iw and Ih (step S500).

  Subsequently, input of image data from the image input unit 601 is started, and data for one stripe of image data to be encoded is stored in the line buffer 602 (step S501).

  Next, the block division unit 603 extracts one tile data from the stripe stored in the line buffer 602 and stores it in the tile buffer 604 (step S502). Subsequently, the lossless encoding unit 103 performs lossless encoding of the tile data stored in the tile buffer 604 (step S503). The code string forming unit 608 combines the tile encoded data output from the lossless encoding unit 103 to generate encoded data to be output from the image processing apparatus in a predetermined format, and sequentially outputs the data to the outside of the apparatus. (Step S605).

  Next, it is determined whether or not the encoded tile is the last tile in the stripe (step S505). If it is not the last tile (NO), the processing target is transferred to the adjacent tile and the processing is repeated from S502. If it is determined that the encoding of the last tile of the stripe has been completed, the process proceeds to step S506. In step S506, it is determined whether or not the encoded stripe is the last stripe of the image. If it is not the last stripe (NO), the process proceeds to step S501 to read the data of the next stripe and read the data of the stripe. Perform the encoding process.

  Thus, if it is determined in step S506 that the encoding of the last stripe has been completed, the encoding process for the image data is terminated.

  With the above processing, the entire image is encoded. Here, although the method of encoding one tile at a time has been described, since the encoding of each tile does not depend on other tiles at all, a plurality of tiles can be encoded in parallel.

  In addition, in order to decode the encoded data generated by the image processing apparatus according to the second embodiment, each tile is decoded in the reverse procedure of the encoding process using the values of T1, T2, and T3 indicated in the header. You should do it. Since each tile is encoded independently, as described above, it is specified by detecting the marker or accessing the encoded data of the tile to be decoded from the length information of the encoded data of each tile. Only tiles can be decoded or multiple tiles can be decoded in parallel.

  As described above, in the image processing apparatus according to the second embodiment, in an encoding method in which an image is divided into tiles and lossless encoding based on predictive encoding is performed independently for each tile, tiles are used. The amount of codes can be reduced by appropriately setting the number of states according to the size of.

  Moreover, the said 2nd Embodiment can be implemented also by running the program which a computer corresponds similarly to the modification of 1st Embodiment. In this case, the computer program includes modules corresponding to the respective configurations as shown in FIG. 6, and the main process may be performed as shown in FIG.

<Other embodiments>
The present invention is not limited to the embodiment described above. For example, although the JPEG-LS Baseline line interleave mode has been described as an example of the lossless encoding method used in the lossless encoding unit 103, other interleave modes of the same standard and other encoding methods based on the context are applied. May be.

  In addition, although the method for determining the number of states based on the total number of pixels R has been shown, an index related to the size of the image (or tile), such as determining from only one of the number of pixels in the horizontal and vertical directions. It may be based on the value.

  In the second embodiment, an example is shown in which an image is divided into tiles and the number of states is determined according to the tile size. However, when one image is divided into several different tiles and encoded. It can also be applied. In this case, the number of states may be determined according to the size of each tile.

  Further, as is clear from the above embodiments, the present invention includes a computer program as a category. Usually, a computer program is stored in a computer-readable storage medium such as a CD-ROM, and It can be executed by copying or installing to the system. Therefore, it is obvious that such a computer-readable storage medium is also within the scope of the present invention.

1 is a block configuration diagram of an image processing apparatus according to a first embodiment. It is a figure which shows a response | compatibility with a difference value and its quantization value. It is a figure which shows the relative positional relationship of the encoding object pixel x and its peripheral pixels a, b, and c. It is a flowchart which shows the encoding process procedure of 1st Embodiment. It is a flowchart which shows the encoding process procedure of 2nd Embodiment. It is a block block diagram of the image processing apparatus which concerns on 2nd Embodiment. It is a figure which shows the basic composition of JPEG-LS encoding data. It is a figure which shows the mode of the tile division | segmentation of an image. It is a figure which shows the structure of the output code sequence of the image processing apparatus which concerns on 2nd Embodiment. It is a figure which shows the structure of the code sequence of one tile of the image processing apparatus which concerns on 2nd Embodiment. It is a figure which shows the structure of the apparatus in the case of implement | achieving by software.

Claims (8)

In the encoded pixel group around the pixel of interest, the difference between the fixed number of pixel pairs is calculated in advance, and the difference value of each calculated pixel pair is quantized. Classifying the surrounding state of the pixel of interest on the basis of, and encoding the pixel of interest according to a probability model corresponding to the classified state,
Quantization parameter setting means for setting a quantization parameter for performing the quantization according to size information indicating a size of an image to be encoded;
Difference calculation means for calculating a difference value of a fixed number of pixel pairs that are in a preset positional relationship in the encoded pixel group around the pixel of interest;
Quantization means for quantizing a difference value of each pixel pair calculated by the difference calculation means according to a quantization parameter set by the quantization parameter setting means;
State determining means for determining the state around the pixel of interest based on the quantized value of each pixel pair obtained by the quantizing means;
An encoding unit that encodes the pixel of interest using the state determined by the state determination unit as an encoding parameter ;
The quantization parameter setting means sets a quantization parameter for reducing the number of values that can be taken after the quantization by the quantization means as the size of the image to be encoded is smaller. Image encoding device. In the encoded pixel group around the pixel of interest, the difference between the fixed number of pixel pairs is calculated in advance, and the difference value of each calculated pixel pair is quantized. Classifying the surrounding state of the pixel of interest on the basis of, and encoding the pixel of interest according to a probability model corresponding to the classified state,
Size setting means for setting the size of a block containing a plurality of pixels;
Cutout means for cutting out the block image data of the block from the image data to be encoded in units of blocks of the size set by the size setting means ;
According to the size information indicating the size of the block set by said size setting means, and a quantization parameter setting means for setting a quantization parameter for performing the quantization,
A difference calculating means for calculating a difference value of a fixed number of pixel pairs in a pre-set positional relationship in the encoded pixel group around the target pixel in the block image data cut out by the cutting means;
Quantization means for quantizing a difference value of each pixel pair calculated by the difference calculation means according to a quantization parameter set by the quantization parameter setting means;
State determining means for determining the state around the pixel of interest based on the quantized value of each pixel pair obtained by the quantizing means;
An encoding unit that encodes the pixel of interest using the state determined by the state determination unit as an encoding parameter ;
The quantization parameter setting means sets a quantization parameter for reducing the number of values that can be taken after the quantization by the quantization means as the block size set by the size setting means is smaller. An image encoding device. The quantization parameter setting means, the horizontal indicated by the size information, based on at least one of the number of vertical pixels, the image encoding apparatus according to claim 1 or 2, characterized that you determine the number of states.   The image encoding apparatus according to claim 1, wherein the encoding unit is a lossless encoding unit using predictive encoding. In the encoded pixel group around the pixel of interest, the difference between the fixed number of pixel pairs is calculated in advance, and the difference value of each calculated pixel pair is quantized. the ambient conditions of the target pixel is classified based on, according to a probability model corresponding to the classified condition, the target pixel to an image coding method for coding,
A quantization parameter setting step for setting a quantization parameter for performing the quantization according to size information indicating a size of an image to be encoded;
A difference calculating step of calculating a difference value of a fixed number of pixel pairs that is in a preset positional relationship in the encoded pixel group around the pixel of interest;
A quantization step of quantizing a difference value of each pixel pair calculated in the difference calculation step according to a quantization parameter set in the quantization parameter setting step;
A state determination step of determining the surrounding state of the pixel of interest based on the quantized value of each pixel pair obtained in the quantization step;
An encoding step of encoding the pixel of interest using the state determined in the state determination step as an encoding parameter ;
The quantization parameter setting step sets a quantization parameter for reducing the number of values that can be obtained after quantization by the quantization step as the size of the image to be encoded is smaller. Image coding method. In the encoded pixel group around the pixel of interest, the difference between the fixed number of pixel pairs is calculated in advance, and the difference value of each calculated pixel pair is quantized. the ambient conditions of the target pixel is classified based on, according to a probability model corresponding to the classified condition, the target pixel to an image coding method for coding,
A size setting step for setting the size of a block containing a plurality of pixels;
A cutout step of cutting out block image data of the block from the image data to be encoded in units of blocks of the size set in the size setting step,
In accordance with size information indicating the size of the block set in the size setting step, a quantization parameter setting step for setting a quantization parameter for performing the quantization,
A difference calculation step of calculating a difference value of a fixed number of pixel pairs in a preset positional relationship in the encoded pixel group around the target pixel in the block image data cut out in the cutout step;
A quantization step of quantizing a difference value of each pixel pair calculated in the difference calculation step according to a quantization parameter set in the quantization parameter setting step;
A state determination step of determining the surrounding state of the pixel of interest based on the quantized value of each pixel pair obtained in the quantization step;
An encoding step of encoding the pixel of interest using the state determined in the state determination step as an encoding parameter;
In the quantization parameter setting step, the smaller the block size set in the size setting step is, the smaller the number of possible values after the quantization in the quantization step is set. A characteristic image encoding method .   A computer program for causing a computer to function as the image encoding device according to claim 1 by being read and executed by the computer.   A computer-readable storage medium storing the computer program according to claim 7.

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