JP2002335407A - Image encoder and image encoding method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To enable high-speed processing when image data of the point sequential system are encoded/decoded while converting the image data into data of the area sequential system. SOLUTION: The image encoder is provided with a pixel value distribution generating means 13 that detects a distribution state of pixel values of image data of the point sequential system, prediction information encoding means 17a-17d that extract a specific prediction information code from the pixel value distribution where any of color components of a pixel is the same as that of peripheral pixels based on the distribution state, error encoding means 18a-18d that extract a prediction error code identified from the pixel value distribution where any of color components of a pixel is different from that of peripheral pixels by each color component, and area code synthesis means 19a-19d that individually synthesize a prediction error code by each color component with a common prediction information code with each color component to obtain encoded data to be decoded to image data adopting the area sequential system.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image encoding apparatus and an image encoding method for encoding image data, in particular, color image data comprising a plurality of color components.

[0002]

2. Description of the Related Art In recent years, personal computers (PCs)
Due to the spread of documents and the like, electronic data conversion of documents is spreading, but the amount of data is increasing several times as much as before (in black and white) with the rapid progress of colorization. Therefore, in order to reduce the data processing load on a colorized document, a color image compression encoding system capable of high speed and high compression is desired.

By the way, as the image data expressing a color image, those of a dot sequential system and those of a frame sequential system are known. The dot-sequential image data is, for example, R
(Red), G (green), B (blue), or Y (yellow),
Each color component such as M (magenta), C (sian), and K (black) is handled collectively. Such point-sequential image data is, for example, CRT (Cathode Rad).
When displaying images in dot-sequential manner on (y Tube), they can be output as they are and can be processed at high speed. On the other hand, image data of the frame sequential method is
Each color component is handled individually, and is often used in, for example, a color printer using electrophotographic technology.

[0004] This means that it is highly necessary to convert the dot-sequential image data handled on the PC into the frame-sequential image data handled on the color printer. At that time, as described above, in order to reduce the processing load, it is desirable to perform encoding on the image data to be converted with high speed and high compression.

Conventionally, as encoding performed when converting dot-sequential image data into frame-sequential image data, for example, encoding performed in a system having a configuration as shown in FIG. 11 is known. That is, in this system, the CPU (Cent
ral processing unit) 31 and, for example, Y, M, C,
The point-sequential image data composed of each color component of K is taken out, converted into the image data of the frame sequential method by the image converter 33, and the encoder group 34 provided individually for each color component is used. Encoding. At this time, each of the encoded data after encoding is individually stored in an HDD (Hard Disk).
Drive) group 35 is temporarily stored. Thereafter, the output control unit 36 outputs the encoded data to each HDD group 3
5, and is decoded using a group of decoders 37 individually provided for each color component, and the decoded data is sent to a color printer 38 for image output.

In addition to this, for example, Japanese Patent Application Laid-Open
Japanese Patent Application Laid-Open No. 336458 proposes, for example, a system having a configuration as shown in FIG. 12 in order to perform high-speed and high-compression encoding while converting dot-sequential image data into frame-sequential image data. According to this system, while following the operation control by the CPU 41, dot-sequential image data composed of, for example, Y, M, C, and K color components stored in advance in the memory 42 is extracted, and is converted into a single code. The encoding is performed using the encoder 43. However, at this time, the encoder 43
In encoding, a predictive information code (for example, run-length identification) specified from the distribution of pixel values in which each of the color components is the same as the surrounding pixels based on the distribution of pixel values in the dot-sequential image data Code) and a prediction error code (for example, a code related to a pixel value at which a run is interrupted) specified from the distribution of pixel values in which one of the color components is different from the surrounding pixels, and a common (single) 3.) The prediction information code and the prediction error code for each color component (for each plane) are individually and temporarily stored in the HDD group 44. Then, when the color printer 45 outputs an image, the output control unit 46 extracts a single prediction information code and a prediction error code for each plane from the HDD group 44 and is provided individually for each color component. The decoder group 47 performs the decoding. Therefore, in this system, the conversion from the dot-sequential system to the frame-sequential system is performed at the same time as internal processing of the encoding, not as preprocessing of the encoding, so that the encoding processing time is shortened.

[0007]

However, in the above-described conventional encoding, when encoding and decoding image data of the dot-sequential system while converting the image data to the frame-sequential system, as described below, It cannot always be said that high-speed processing can be performed for both encoding and decoding.

For example, in the encoding in the system shown in FIG. 11, it is necessary to convert the dot-sequential image data into the frame-sequential system as pre-processing of the encoding, so that it is difficult to shorten the encoding processing time. It is. In addition, since it is necessary to provide the encoder group 34 individually for each color component, the configuration becomes complicated, and as a result, it becomes difficult to reduce the size and cost of the system.

Also, in the encoding in the system disclosed in, for example, Japanese Patent Application Laid-Open No. 10-336458 (see FIG. 12), since the point-sequential system is converted to the frame-sequential system at the time of encoding, the encoding processing time is reduced. , But
Rapid decoding as in the system shown in FIG. 11 cannot be realized. This is because the decoding requires both a single prediction information code and a prediction error code for each plane. Therefore, when decoding a certain plane, the output control unit 46 converts the prediction information code and the prediction error code into two. This is because it is necessary to switch and take out the data from the HDD group 44, thereby reducing the processing efficiency of the decoding operation.

In particular, recently, some color printers include:
There is a so-called tandem machine in which engines corresponding to Y, M, C, and K color components can operate in parallel. When an image is output by such a tandem machine, decoding processing is performed. The reduction in efficiency becomes remarkable. That is, in the case of a tandem machine, since a plurality of planes are simultaneously image-outputted, a single prediction information code may be simultaneously extracted for decoding processing of each plane. It is conceivable that the load applied to the HDD 46 and the HDD group 44 becomes four times as large as that of the normal case, and the efficiency is further reduced.

Therefore, the present invention provides a high-speed processing for both encoding and decoding even when the encoding and decoding are performed while converting the dot-sequential image data to the frame sequential system. It is an object of the present invention to provide an image encoding device and an image encoding method which can perform the following.

[0012]

SUMMARY OF THE INVENTION The present invention is an image encoding device devised to achieve the above object. That is, an image encoding apparatus that encodes point-sequential image data in which color components are collectively handled so as to be decoded as frame-sequential image data in which each color component is individually treated, A pixel value distribution generating means for detecting the distribution state of pixel values in the image data of the sequential method, and a pixel value distribution in which each of the color components is the same as the peripheral pixel based on the extraction result of the pixel value distribution generating means. Prediction information encoding means for extracting a prediction information code specified from the distribution,
Error encoding means for extracting, for each color component, a prediction error code specified from a distribution of pixel values in which any of the color components is different from peripheral pixels based on the extraction result in the pixel value distribution generating means; The prediction error code for each color component extracted by the encoding unit is individually combined with a common prediction information code for each color component extracted by the prediction information encoding unit, and the encoded data for each color component after the combination is combined. And a plane code synthesizing means for converting encoded data into image data which can be decoded into the image data of the plane sequential method.

Further, the present invention is an image coding method devised to achieve the above object. That is, the image data of the dot sequential method in which each color component is collectively treated is
An image encoding method for encoding each color component so that it can be decoded as plane-sequential image data that is individually treated, based on the distribution of pixel values in the dot-sequential image data, A prediction information code specified from a distribution of pixel values each of which is the same as a peripheral pixel, and an error specified from a distribution of pixel values in which any of the color components are different from the peripheral pixel are extracted, and the error is determined for each color. In addition to classifying the prediction error code for each component, the prediction error code for each color component is individually synthesized with a common prediction information code for each color component, and the encoded data for each color component after the synthesis is subjected to the above-described frame sequential. It is characterized in that it is coded data that can be decoded into image data of the system.

According to the image encoding apparatus and the image encoding method having the above-described configuration, a prediction information code and a prediction error code are extracted from the distribution of pixel values in dot-sequential image data. Instead of treating them separately, the prediction error code for each color component is individually combined with the common prediction information code for each color component, so if the encoded data for each color component after the combination is decoded, the frame sequential method Is obtained. Therefore, the conversion from the dot-sequential system to the frame-sequential system is performed simultaneously as internal processing of the coding, not as a pre-process of the coding. Therefore, the conversion from the dot-sequential system to the frame-sequential system is performed in advance. It is not necessary to perform the encoding or to individually encode each color component. In addition, when decoding to obtain image data of the frame sequential method, it is only necessary to decode the coded data for each color component after synthesis, so both the prediction information code and the prediction error code are required for each color component. There is no such thing as.

[0015]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, an image encoding apparatus and an image encoding method according to the present invention will be described with reference to the drawings.

First, a schematic configuration of the image encoding device will be described. FIG. 1 is a block diagram illustrating an example of a schematic configuration of a color image encoding / decoding device including an image encoding device according to the present invention, and FIG. 2 is a configuration example of a system using the color image encoding / decoding device. FIG.

The color image encoding / coding described in the present embodiment
The decoding device is used, for example, in a system as shown in FIG. According to this system, while following the operation control by the CPU 1, dot-sequential image data composed of, for example, Y, M, C, and K color components stored in advance in the memory 2 is extracted and is converted into a single code. Encoder 3 for encoding. By this encoding, H corresponding to each color component
In the DD group 4, coded data for each color component coded as described in detail later is temporarily stored and stored. However, it goes without saying that the coded data may be stored and stored not in the HDD group 4 but in a general-purpose storage device such as a RAM (Random Access Memory). And
When the color printer 5 outputs an image, the output control unit 6 extracts encoded data for each color component from the HDD group 4 or a general-purpose storage device (hereinafter, these are referred to as “HDD group 4 etc.”) and The decoder group 7 individually provided for each component performs the decoding. The above processing is repeated until there is no more image data to be output. Usually, the repetition is performed in a predetermined processing unit, for example, one page unit. In this system, the encoder 3 and the decoder group 7 correspond to the color image encoding / decoding device described in the present embodiment, and the encoder 3 corresponds to the image encoding device according to the present invention. Shall be.

The system configured as described above has the following three major features. That is, (1) since the conversion from the dot-sequential system to the frame-sequential system is performed not as preprocessing of encoding but as internal processing of the encoder 3, the time required for the point-sequential / plane-sequential image conversion is reduced. Is done. (2) In encoding, instead of comparing pixel values for each plane in the frame sequential system, pixel values are compared in the dot sequential system at the same time on the entire surface, so that the number of times of pixel value comparison and prediction information encoding is reduced. Is done. Furthermore, (3) since the encoded data after encoding is an independent code for each plane, control during decoding is simplified, and rapid decoding can be performed.

Next, the configuration of a color image encoding / decoding device for realizing these features will be described. The color image encoding / decoding device described in the present embodiment has the configuration shown in FIG.
As shown in (1), it is roughly divided into an encoding unit and a decoding unit.

The encoding unit corresponds to a buffer 11, a reference address generator 12, an identical pixel value distribution generator 13, a prediction information generator 14, a point forward image converter 15, and each color component. A plurality of surface pixel comparators 16a, 16
, b, 16c, 16d..., a plurality of prediction information encoders 17a, 17b, 17c, 17d..., and a plurality of error calculation encoders 18a, 18b, 18c, 18d.
Similarly, a plurality of plane code synthesizers 19a, 19b, 19
c, 19d...

The buffer 11 temporarily stores dot sequential image data to be encoded.

The reference address generator 12 includes a buffer 11
For example, pixel values of a pixel to be noted in the encoding process (hereinafter referred to as “pixel of interest”) and a plurality of pixel values in a peripheral area thereof are obtained from dot-sequential image data extracted one pixel at a time in the raster scanning order. And outputs these as target pixel data and reference area data, respectively. Since the reference address generator 12 performs processing on dot-sequential image data, there is only one reference address generator irrespective of the number of image planes.

The same pixel value distribution generator 13 determines how the pixels having the same pixel value as the target pixel are distributed around the target pixel based on the target pixel data and the reference area data from the reference address generator 12. Is detected,
The result is output as the same pixel value distribution.
Since the same pixel value distribution generator 13 also performs processing on the image data of the dot-sequential system, it suffices that there be only one regardless of the number of planes of the image.

The prediction information generator 14 determines whether or not the target pixel data can be coded only by the same pixel value distribution from the same pixel value distribution generator 13. It is determined whether or not encoding is performed with reference to the same pixel, and this is output as prediction information. If encoding is impossible, information that encoding is impossible is generated and output.

The point-sequential plane-sequential image converter 15 converts each pixel data of the point-sequential system into a plane-sequential system and outputs the data as pixel data of the plane-sequential system. However, in the point-sequential surface-sequential image converter 15, the prediction information generator 14 determines that the pixel data that cannot be encoded by the same pixel value distribution alone is the same as the raster scanning order in a series of pixel data groups as a processing unit. Performs the conversion only on the first pixel data.

Surface pixel comparators 16a, 16b, 16c, 1
.. 6d... Temporarily store the pixel data of the plane sequential system converted by the point-sequential plane-sequential image converter 15 for each color component. The data are compared with each other to determine whether or not they are the same. However, the surface pixel comparators 16a, 1
6b, 16c, 16d,..., The determination is made only when the prediction information generator 14 determines that encoding is impossible only with the same pixel value distribution.

The prediction information encoders 17a, 17b, 17
When the prediction information generator 14 determines that the encoding can be performed only by the same pixel value distribution, c, 17d... perform encoding according to the prediction information generated by the prediction information generator 14,
The result is output as a prediction information code. Further, the prediction information encoders 17a, 17b, 17c, 17
are determined as impossible to encode by the prediction information generator 14, but the plane pixel comparators 16a, 16b, 16c, 1
If it is determined by 6d that encoding is possible for each plane, encoding is performed for each plane, and the result is output as a prediction information code.

Error calculation encoders 18a, 18b, 18
., c, 18d... indicate that the prediction information generator 14 cannot perform encoding using only the same pixel value distribution, and the surface pixel comparator 1
When it is determined that encoding for each plane is impossible, 6a, 16b, 16c, 16d,... Also calculate a prediction error, further perform, for example, arithmetic coding, and output the result as a prediction error code.

Surface code synthesizers 19a, 19b, 19c, 1
9d are prediction information encoders 17a, 17b, 17c,
17d and the prediction error codes output from the error calculation encoders 18a, 18b, 18c, 18d... Are combined as independent encoded data for each surface (each color component). Output.

In contrast to such an encoding unit, the decoding unit provides the plane code decoders 21a, 21b, 21c,
21d, and predicted pixel generators 22a, 22b, 22c,
22d, and error adders 23a, 23b, 23c, 23
d ... are provided.

The plane code decoders 21a, 21b, 21c, 2
1d are surface code synthesizers 19a, 19b, 1 of the encoding unit.
9c, 19d... Are separated and decoded into a prediction information code and a prediction error code, the prediction information is output in the case of the prediction information code, and the prediction information is output in the case of the prediction error code. It outputs an error value.

The predicted pixel generators 22a, 22b, 22c,
22d are the plane code decoders 21a, 21b, 21c, 2
1d generate and output a predicted pixel value corresponding to the separated / decoded prediction information.

The error adders 23a, 23b, 23c, 23
d ... are the plane code decoders 21a, 21b, 21c, 21d
Are separated and decoded by the prediction pixel generator 22a,
22b, 22c, 22d,... Are added to the generated predicted pixel values and output as pixel value data.

Next, an example of a processing operation in the color image encoding / decoding device configured as described above will be described. First, an operation example at the time of encoding will be described.

FIG. 3 is an explanatory diagram showing an example of dot-sequential image data to be encoded. As shown in the example,
The dot sequential image data is, for example, a set of pixel data obtained by scanning one page, which is a processing unit, in the order indicated by the arrow in the drawing. At this time, each pixel data is composed of a plurality of component data (three components in the illustrated example) corresponding to each color component. That is, because of the dot-sequential method, component data for each color component is collectively handled. For example, if the image data is Y, M, C, K
, Each pixel data is composed of four component data corresponding to each color component.
If each component is 8 bits, it is represented by 8 bits × 4 colors = 32 bits.

When performing encoding processing on such dot-sequential image data, the reference address generator 12
Extracts the pixel data one by one from the buffer 11 one by one, extracts the pixel value of the target pixel and the pixel values of its peripheral pixels, and specifies these as the target pixel data and the reference area data, respectively. FIG. 4 is an explanatory diagram of a specific example of the arrangement of the target pixel and its peripheral pixels. As shown in the example of the figure, the surrounding pixels are four pixels around the pixel of interest (upper left,
Right above, upper right, next to left). It is assumed that the position of the target pixel sequentially moves in the scanning order shown in FIG.

Based on the target pixel data and the reference area data specified by the reference address generator 12, the same pixel value distribution generator 13 determines that the reference area data has the same pixel value as the target pixel data. Are compared, and the result is output as the same pixel value distribution. For example, the same pixel value distribution generator 13 replaces peripheral pixel data having the same pixel value as the target pixel data with “1” and peripheral pixel data that is not the same with “0”, and collects the replaced four peripheral pixels. To output the same pixel value distribution.
Therefore, for example, in the case of the specific example shown in FIG.
"1" immediately above and to the left of the pixel of interest is "0"
The same pixel value distribution as follows is generated.

At this time, "1" is included in the same pixel value distribution.
That is, if there is at least one peripheral pixel having a pixel value equal to the pixel value of interest, encoding can be performed only with the same pixel value distribution. Therefore, the prediction information generator 14 refers to the same pixel at any position. It is determined whether or not to perform encoding, and this is output as prediction information. On the other hand, when the same pixel value distribution is all “0”, the prediction information generator 14 determines that encoding is impossible only with the same pixel value distribution, and generates information indicating that encoding is impossible. Output.

The processing up to this point is performed for each piece of pixel data of the dot sequential method, that is, for example, for each piece of 32-bit pixel data composed of a plurality of component data. The processing is performed on the pixel data of the frame sequential method.

FIG. 6 is a block diagram showing an example of a point-by-plane image converter. As shown in FIG.
When pixel data is input in a 32-bit dot-sequential system, the pixel data is sequentially converted from the upper 8 bits, for example, to K
The image data is divided into pixel data of each surface of Y, M, and C, and each is output to the surface pixel comparators 16a, 16b, 16c, 16d,. However, the point-sequential plane-sequential image converter 15 determines that such a conversion is not possible by the prediction information generator 14 with the pixel data having the first raster scanning order in one page as a processing unit. This is performed only for the pixel data for which the sign to that effect has been output.

When the point-by-plane sequential image converter 15 converts the first pixel data of one page, the pixel data of each plane after the conversion is converted into the plane pixel comparators 16a and 16a.
., 16c, 16d,...
6a, 16b, 16c, 16d,... Are temporarily held. Thereafter, when the prediction information generator 14 determines that encoding is possible only with the same pixel value distribution and outputs prediction information for the pixel data in the next raster scanning order,
The point-sequential plane-sequential image converter 15 does not convert the pixel data from the point-sequential system to the plane-sequential system. However, it goes without saying that it may be performed.

The prediction information output from the prediction information generator 14 is output to the plane pixel comparators 16a, 16b, 16c,
16d ... predictive information encoders 17a, 17b, 17
c, 17d... Thus, the prediction information encoders 17 a, 17 b, 17 c, 17 d,... For the next pixel data of the first pixel data are based on the pixel value of the first pixel data and the prediction information from the prediction information generator 14. Prediction coding can be performed.

At this time, the prediction information encoders 17a, 17
It is conceivable that b, 17c, 17d,... perform encoding in accordance with a preset reference pixel label and a code generation table. Examples of the reference pixel label and the code generation table include, for example, specific examples shown in FIG. According to this specific example, if “A” in the reference pixel label shown in FIG. 7A matches the target pixel value, the prediction information code is changed from the code generation table shown in FIG. 1 ". When “A” and “B” of the reference pixel labels do not match but “C” does, the prediction information code is “001”.

When the prediction information generator 14 outputs information indicating that encoding is impossible only with the same pixel value distribution for the pixel data in the raster scanning order and thereafter, the point-sequential plane-sequential image conversion is performed each time the information is output. The unit 15 converts the pixel data from the dot-sequential system to the plane-sequential system, and converts the pixel data of each plane after the conversion into the plane pixel comparators 16a, 16b, 16c,
16d...

Then, the surface pixel comparators 16a, 16b, 1
.. 6c, 16d... Compare the pixel data received from the point-by-plane sequential image converter 15 with the pixel data already received and temporarily stored, and can encode the pixel data received later. Is determined. This determination may be made based on the result of comparison between pixel data. For example, if the same pixel value continues, it may be determined that encoding is possible.

If it is determined that encoding is possible, the surface pixel comparators 16a, 16b, 16c, 16d,...
b, 18c, 18d..., but not the prediction information encoder 17
a, 17b, 17c, 17d,... and encoded by the prediction information encoders 17a, 17b, 17c, 17d,. Note that the encoding method at this time may be performed in the same manner as that based on the prediction information from the prediction information generator 14, or a well-known method such as run-length encoding may be used.

On the other hand, if it is determined that encoding is impossible,
The surface pixel comparators 16a, 16b, 16c, 16d,...
a, 18b, 18c, 18d... That is, the prediction information generator 14 determines that encoding is not possible only with the same pixel value distribution, and the area pixel comparators 16a, 16b, 16
.., 16 d... only when it is determined that encoding for each plane is not possible,
18b, 18c, 18d...

Then, the error calculation encoders 18a, 18
., b, 18c, 18d,... cannot perform encoding on the received pixel data using the peripheral pixel values as they are, calculate a prediction error, further perform, for example, arithmetic coding, and output this as a prediction error code. I do. The arithmetic expression used for the arithmetic coding at this time is, for example, a specific example shown in FIG.

As described above, the prediction information encoder 17
a, 17b, 17c, 17d... output prediction information codes, and error calculation encoders 18a, 18b, 18c, 18
are output to the plane code synthesizers 19a, 19b, 19c, 19d, and so on, and are output to the plane code synthesizers 19a, 19b, 19c, and 19d.
d ... are synthesized. At this time, the plane code synthesizer 19a,
19b, 19c, 19d,... May be composed of a prediction error code followed by a prediction error code, as in the specific example shown in FIG.

Thus, the plane code synthesizers 19a, 19
b, 19c, 19d..., the combined result of the prediction information code and the prediction error code is output as independent coded data for each plane (each color component), that is, a single code data stream. .

Surface code synthesizers 19a, 19b, 19c, 1
The encoded data output from 9d...
The data is written in a predetermined area such as the DD group 4. However, the writing at this time does not have to wait until the encoded data on the entire surface is completed, and may be performed from the completed surface. Plane code synthesizer 1
9a, 19b, 19c, 19d... Are provided individually corresponding to the respective surfaces, and the HDD group 4 and the like are also provided individually corresponding to the respective surfaces.

Here, an example of the operation at the time of encoding as described above will be described in more detail with a specific example. In addition,
Here, the dot-sequential image data to be encoded is composed of Y, M, C, and K color components, and pixel data corresponding to each color component is represented by 2 bits × 4 colors = 8 bits. Take the case as an example. Furthermore, in order to simplify the description, a description will be given of a run-length method as an encoding method. However, the encoding method is not limited to the run-length method, and it goes without saying that encoding based on the same pixel value distribution can be applied as described above. FIG. 10 is an explanatory view showing a specific example of dot-sequential image data to be encoded and its encoding result.

For example, as shown in FIG. 10A, the pixel value of the K color component is “1” and the pixel values of the other color components are “0”.
The pixel data that is the same as the pixel data “A” is continuous for three pixels in the raster scanning order. Thereafter, the pixel data of which the pixel values of all the color components are “0” are sandwiched by one pixel, and the pixel data “A” is again displayed.
Let us consider a case where the same pixel data continues for two pixels in raster scanning order.

At this time, since the prediction information generator 14 determines whether or not encoding is possible in pixel data units of the dot sequential method, prediction is performed based on only prediction information output from the prediction information generator 14. Information encoders 17a, 17b, 1
7c, 17d... And error calculation encoders 18a, 18
.. perform encoding, b, 18c, 18d.
As a result, encoded data for each color component as shown in FIG. That is, “A” means that the same pixel value continues for three pixels from the pixel data “A” for each color component.
A code consisting of a code “3”, a code “E” meaning that the pixel value is different and a code consisting of the error value “1” or “0”, and again the same pixel value from the pixel data “A” is 2 Coded data consisting of a code “A3” meaning that pixels are continuous is obtained.

However, focusing on each of the Y, M, and C color components, the same pixel value of “0” is continuous for all of these pixel values. Therefore, even when the prediction information generator 14 determines that encoding is impossible,
The surface pixel comparators 16a, 16b, 16c, 16d,... Temporarily hold the pixel values received from the point-by-point surface sequential image converter 15, and compare the pixel values with newly received pixel values. Then, it is determined whether encoding is possible for each color component.

Thus, the prediction information encoders 17a, 1
7b, 17c, 17d... And error calculation encoder 18
a, 18b, 18c, 18d,...
Not only the prediction information output from the
Since it is also based on the determination result of whether or not encoding is possible for each color component by a, 16b, 16c, 16d,.
When encoding is performed on each pixel data shown in FIG. 10A, encoded data for each color component as shown in FIG. 10C is obtained. That is, for the K color component, FIG.
This is the same as the case shown in FIG. 0 (b), but for each color component of Y, M and C, as shown in FIG. 10 (c), the same pixel value as the pixel data “A” continues for six pixels. This is represented only by the symbol “A6”.

Next, an example of the operation at the time of decoding the encoded data generated as described above will be described.

At the time of decoding, first, in FIG.
U1 reads the encoded data of the entire surface of each color component in HD
An instruction is given to D group 4 and the like. In response, HDD group 4
And the like read the encoded data stored therein and temporarily store it in the memory 2. When the storage in the memory 2 is completed, the CPU receiving the notification
1 notifies the output control unit 6 that the encoded data is prepared in the memory 2. Thereby, the output control unit 6
Starts the decoder group 7, that is, the decoding unit of the color image encoding / decoding device, according to the output timing of the color printer 5.

When the decoding unit is activated, in FIG. 1, first, the plane code decoders 21a, 21b, 21c, 21d...
Separates the encoded data received from the memory 2 into a prediction information code and a prediction error code under the control of the output control unit 6. At this time, if the separated data is a prediction information code, the plane code decoders 21a, 21b, 21c, 2
1d are prediction information encoders 17a, 17b, 17c,
Decoding is performed by a decoding method corresponding to the coding method of 17d, and is output as prediction information. On the other hand, if the separated data is a prediction error code, the error calculation encoder 18a,
.. Are decoded by a decoding method corresponding to the coding method of 18b, 18c, 18d, and output as an error value.

Then, the plane code decoders 21a, 21b, 2
When the prediction information is output from 1c, 21d, etc., the prediction pixel generators 22a, 22b, 22c, 22d,... Generate and output the corresponding prediction pixel values from the prediction information. For example, when the label information shown in FIG. 7 is decoded as the prediction information, the pixel value of the pixel at the position corresponding to the label is output as the prediction pixel value. When the error values are output from the plane code decoders 21a, 21b, 21c, 21d,.
3b, 23c, 23d,... Add the error value to the predicted pixel values generated by the predicted pixel generators 22a, 22b, 22c, 22d, and output these as pixel value data.

When the pixel data for each surface is decoded in this way, the decoding unit sequentially outputs the decoded pixel data to the color printer 5. Then, the above processing is repeated until there is no more data to be output. As a result, the color printer 5 prints out the image data of the frame sequential method as a visible image on paper, for example.

As described above, in the present embodiment, the prediction information code and the prediction error code are extracted from the distribution state of the pixel values in the dot sequential image data. Based on the prediction information output from the generator 14, the prediction information encoders 17a, 17b,
., 17c, 17d,..., And a common predictive information code for each color component, and an error calculation encoder 18a, 18d for each color component.
., 18c, 18d...
The plane code synthesizers 19a, 19b, 19c, 19d,... Synthesize as independent encoded data for each plane (each color component).

Therefore, according to this embodiment, if the encoded data for each color component after the synthesis is decoded, the image data of the frame sequential system can be obtained. (1) Conversion from the dot sequential system to the frame sequential system Are performed simultaneously as internal processing of encoding, not as preprocessing for encoding. Therefore, it is not necessary to perform conversion from the dot-sequential system to the frame-sequential system in advance, or to individually perform encoding for each color component, and it is possible to reduce the time required for the dot-sequential / plane-sequential image conversion. .

(2) In encoding, pixel values are not compared for each plane of the frame sequential system, but are compared at the same time in the dot sequential system. In other words, detection of the same pixel value distribution and prediction information encoding based on the same can be performed at once without depending on the number of image planes. This makes it possible to reduce the number of times of pixel value comparison and encoding of prediction information, and as a result, the encoding processing time can be reduced. Moreover, the reference address generator 12
In addition, since only one identical pixel value distribution generator 13 is required irrespective of the number of planes of the image, the circuit configuration can be simplified.

Further, (3) since the encoded data after encoding is an independent code for each plane, the control at the time of decoding is simplified, and rapid decoding can be performed. That is, in decoding for obtaining image data of the frame sequential method, it is only necessary to decode the coded data for each color component after synthesis, so both the prediction information code and the prediction error code are required for each color component. There is no such thing as.

In particular, in the present embodiment, the prediction information encoders 17a, 17b, 17c, 17d... And the error calculation encoders 18a, 18b, 18c, 18d. In addition, the determination is made based on the determination result of whether or not encoding is possible for each color component by the surface pixel comparators 16a, 16b, 16c, 16d,. That is, the prediction information encoders 17a, 17b, 17
Prior to the coding by c, 17d,..., the surface pixel comparators 16a, 16b, 16c, 16d... Are extracted from the pixel value distribution, and the prediction information encoders 17a, 17b, 17c, 17d... Perform encoding based on the extracted prediction information. Therefore, as described with reference to FIG. 10, for example, even if it is determined that encoding is not possible in a dot-sequential pixel data unit, it is possible to further determine whether encoding is possible for each color component. As a result, more efficient encoding (reduction of data amount) can be realized.

In this embodiment, the case where the image data to be encoded mainly consists of the Y, M, C, and K color components has been described. However, other image data such as RGB and L ^* a ^* b ^* may be used. It goes without saying that the same applies to image data in a color space.

[0068]

As described above, according to the image encoding apparatus and the image encoding method of the present invention, the encoding / decoding of the dot-sequential image data is performed while the image data is converted to the frame sequential method. Even in the case where it is performed, high-speed processing can be performed for both encoding and decoding.

[Brief description of the drawings]

FIG. 1 is a block diagram illustrating an example of a schematic configuration of a color image encoding / decoding device including an image encoding device according to the present invention.

FIG. 2 is a schematic diagram illustrating a configuration example of a system using the color image encoding / decoding device of FIG. 1;

FIG. 3 is an explanatory diagram showing an example of dot sequential image data to be encoded;

FIG. 4 is an explanatory diagram showing a specific example of an arrangement of a target pixel and its peripheral pixels.

FIG. 5 is an explanatory diagram showing a specific example of a reference region and the same pixel value distribution.

FIG. 6 is a configuration diagram illustrating an example of a point-sequential surface sequential image converter.

FIG. 7 is an explanatory diagram showing a specific example of a reference pixel label and a code generation table used in the encoding process;
(A) is a diagram showing a reference pixel label, and (b) is a diagram showing a code generation table.

FIG. 8 is an explanatory diagram showing a specific example of an arithmetic expression for error calculation encoding used in the encoding process.

FIG. 9 is a configuration diagram showing a specific example of a configuration of encoded data.

FIG. 10 is an explanatory diagram showing a specific example of dot-sequential image data to be encoded and an encoding result thereof;
(A) is a diagram of a specific example of image data, and (b) and (c) are diagrams of a specific example of an encoding result thereof.

FIG. 11 is a schematic diagram (part 1) illustrating a configuration example of a system using a conventional color image encoding / decoding device.

FIG. 12 is a schematic diagram (part 2) illustrating a configuration example of a system using a conventional color image encoding / decoding device.

[Explanation of symbols]

3: Encoder, 12: Reference address generator, 13: Same pixel value distribution generator, 14: Prediction information generator, 15: Point-by-plane forward image converter, 16a, 16b, 16c, 16d: Surface pixel comparison , 17a, 17b, 17c, 17d ... prediction information encoders, 18a, 18b, 18c, 18d ... error calculation encoders, 19a, 19b, 19c, 19d ... surface code synthesizers

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 5C057 BA07 BA14 EM01 EM07 EM13 FB03 FE03 5C059 LA06 ME05 PP14 TA02 TB04 TC02 TC03 TC42 TD09 UA02 UA34 5C078 AA09 BA32 CA31 DA00 DA01 DA02 DB16

Claims (4)

[Claims] 1. An image encoding apparatus for encoding point-sequential image data in which color components are collectively handled so as to be decoded as frame-sequential image data in which each color component is individually handled. A pixel value distribution generating means for detecting a distribution state of pixel values in the dot-sequential image data; and all of the respective color components are the same as peripheral pixels based on an extraction result by the pixel value distribution generating means. A prediction information encoding unit that extracts a prediction information code specified from the pixel value distribution; and, based on an extraction result obtained by the pixel value distribution generation unit, a pixel value distribution in which one of the color components is different from the surrounding pixels. Error encoding means for extracting a specified prediction error code for each color component; and a prediction error code for each color component extracted by the error encoding means for each color component extracted by the prediction information encoding means. And a plane code synthesizing means for individually synthesizing the common prediction information code with each other and converting the encoded data for each color component after the synthesis into encoded data that can be decoded into the image data of the frame sequential method. An image encoding device characterized by the above-mentioned. 2. Prior to the error encoding means extracting a prediction error code, a pixel value in which one of each color component is different from a peripheral pixel is specified from a distribution of pixel values identical to the peripheral pixel for each color component. 2. The image code according to claim 1, further comprising: an individual prediction information encoding unit that extracts the individual prediction information code to be extracted, and combines the individual prediction information code with the prediction information code and the prediction error code. Device. 3. An image encoding method for encoding point-sequential image data in which color components are collectively handled so as to be decoded as plane-sequential image data in which each color component is individually treated. A prediction information code specified from a distribution of pixel values in which each of the color components is the same as a peripheral pixel, based on the distribution of pixel values in the dot-sequential image data; A pixel and an error specified from a distribution of pixel values different from the pixel are extracted, and the error is separated into a prediction error code for each color component, and a prediction error code for each color component is shared with a prediction information code common to each color component. An image encoding method, wherein the encoded data is individually combined, and the encoded data for each color component after the combination is encoded data that can be decoded into the image data of the frame sequential method. 4. Prior to extracting the prediction error code, individual prediction information specified from a distribution of pixel values identical to the peripheral pixels for each color component for a pixel value in which one of the color components is different from the peripheral pixel. 4. The image encoding method according to claim 3, wherein a code is extracted and combined with the prediction information code and the prediction error code.