JP4006351B2 - Image processing method, image processing apparatus, computer program, and computer-readable storage medium - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a technique for compressing and encoding image data.
[0002]
[Prior art]
Conventionally, many methods have been proposed for improving the coding efficiency by dividing image information into a plurality of regions and applying a coding method (hybrid coding method) suitable for each region. Yes.
[0003]
Here, as the type of encoding employed in hybrid encoding, JPEG encoding is performed for halftone areas such as natural images captured by a digital camera, and run-length encoding is performed for areas such as characters and line drawings. It will be general.
[0004]
[Problems to be solved by the invention]
Incidentally, some recent printers have a recording resolution exceeding 1000 dpi, and the amount of image data output from the host computer to the printer is large. In particular, in the case of a color printer, the number of color components increases and the amount of information becomes enormous. Therefore, it is desirable to apply the hybrid encoding method as described above to such a printing system.
[0005]
When considering such a system, for example, when the printer is an ink jet printer, for example, the carriage on which the recording head is mounted is basically scanned and printed, so at least the printer is used. Needless to say, a memory for developing a recorded image for one scan is required, but a buffer memory sufficient for decoding processing is required.
[0006]
The present invention intends to provide a technique for reducing the amount of memory required for decoding encoded image data in which lossless encoded data and lossy encoded data are mixed.
[0007]
[Means for Solving the Problems]
In order to solve this problem, for example, the image processing method of the present invention includes the following steps. That is,
An image processing method for encoding image data in units of pixel blocks,
A first encoding step of encoding the image data with a first encoding algorithm;
A step of determining whether or not to perform the first encoding step for each pixel block of the image data;
A first accumulating step of temporarily accumulating encoded data of the pixel block obtained by encoding in the first encoding step when it is determined in the determining step that encoding is performed in the first encoding step; When,
A replacement step of replacing all pixel values in the pixel block to be encoded in the first encoding step with a preset value;
A second encoding step of encoding the pixel block after the replacement and a pixel block determined not to be performed in the first encoding step in the determination step with a second encoding algorithm;
An output step of outputting the encoded data accumulated in the first accumulation step after being delayed by a preset unit from the encoded data obtained by encoding in the second encoding step. .
[0008]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments according to the present invention will be described in detail with reference to the accompanying drawings.
[0009]
First, the outline of the hybrid coding method examined by the present inventors will be described.
[0010]
FIG. 1 shows a block diagram of a hybrid encoding method by the present inventors. In the figure, as a plurality of encoding methods applied to an image, two types of run-length encoding 102 which is a lossless encoding method and JPEG encoding unit 103 which is an irreversible encoding method are prepared. An image input from the input terminal 100 is first subjected to plane division processing in the plane division unit 101. Specifically, the image is divided into small blocks of arbitrary size (for example, 8 × 8 square blocks, hereinafter referred to as pixel blocks), and the pixel blocks are divided into the two kinds of encoding methods according to predetermined conditions. Of these, it is determined which encoding should be performed. For example, the difference between the maximum and minimum density values in a block is obtained, and if this difference is greater than a certain value, it is considered that the block contains a character part or an edge part, and such a block has no distortion. Encoding (reversible encoding), that is, in the example of FIG. 1, the run-length encoding unit 102 performs encoding. If the above conditions are not met, JPEG encoding with a higher compression ratio is performed although it is irreversible. Note that the run-length encoding and JPEG encoding algorithms are widely known, and thus detailed description thereof is omitted here.
[0011]
FIG. 2 shows a conceptual diagram of plane division processing. Since JPEG is used in the example of FIG. 1, in FIG. 2, an image is divided into pixel blocks, and plane division processing is performed for each block. In the figure, blocks indicated by diagonal lines are blocks that are determined to be subjected to JPEG encoding by the determination. Such a block is extracted from the original image, and forms a JPEG plane as indicated by 201 different from the original image. Note that the corresponding region (8 × 8 pixel region) of the original image from which the block is extracted is filled with an arbitrary value, for example, (R, G, B) = (255,255,255) to be a run-length plane. As a result, the efficiency of run-length encoding is increased to the limit for the region at the pixel block position determined to be encoded by JPEG.
[0012]
Two pieces of image information (planes) generated by such processing are input to the run-length encoding unit 102 and the JPEG encoding unit 103, respectively, and compressed and encoded.
[0013]
The compression-coded data is input to the format forming unit 110, and after the format as shown in FIG. 3 is formed, it is output from the output terminal. In the format shown in the figure, three types of data, run-length data, JPEG block position information, and JPEG data, are alternately transferred for each raster unit shown in FIG. 2 (in units of 8 lines). ing. Here, the JPEG block position information is 1-bit identification information assigned to each block shown in FIG. 2, and “1” is assigned to the blocks classified as JPEG planes by the plane dividing unit 101. “0” is assigned to a block classified as a run-length plane. With this 1-bit information, the decoding side can synthesize the decoded JPEG block on the run-length plane.
[0014]
The output image information is stored in a storage device such as a memory or a hard disk, or transferred to another computer or device via a communication path.
[0015]
As an apparatus for receiving and decoding the encoded data generated by the above processing, for example, a printer having a configuration as shown in FIG. 4 is considered. Here, 400 is a printer apparatus, 401 is a CPU that controls the entire apparatus, and 402 is a ROM that stores a program for performing printing processing (including decoding processing). A RAM 403 is used as various buffers and a work area for the CPU 401. Reference numeral 404 denotes an interface for receiving print data (image data compressed and encoded by the hybrid encoding method) from the host computer, and reference numeral 405 denotes a printer engine that discharges ink droplets. However, the printing method is not limited to this, and other methods may be used.
[0016]
FIG. 5 schematically shows a function related to the decoding process in the configuration of FIG. The configuration described below is easy to understand when it is considered to be a program module, but of course, it may be realized by hardware.
[0017]
In FIG. 5, among the encoded information input from the input terminal 500, run-length and JPEG encoded data are input to the respective decoding units, and the decoding process of each plane is performed. Next, the plane synthesis unit 509 reconstructs the original image by synthesizing each block of the decoded JPEG plane with the decoded run-length plane.
[0018]
The hybrid encoding and decoding method can be applied to various applications. For example, the encoding method is applied to a part of a printer driver in a host computer, and processing using the decoding method is performed in a printer. It is possible to reduce the amount of information by applying to image data flowing between the two.
[0019]
By the way, in some run-length encodings, there is one in which the position of a reference pixel for comparing whether or not it is the same as a target pixel to be encoded has an upper position in addition to the left as shown in FIG. That is, there is a run-length encoding that compares the target pixel with an arbitrary position above not only on the left side but outputs the number of consecutive pixels as a code if they have the same density value. Furthermore, the reference pixel position is not necessarily adjacent to the target pixel, and as shown in FIG. In such a case, a buffer memory for storing the decoded JPEG block is also required in addition to the buffer memory for storing the composite result image in the decoding device.
[0020]
FIG. 7 illustrates the above problem. This figure shows the use status of the buffer memory inside the decoding apparatus. 700 is a buffer memory for storing the final composite image, and 701 is a buffer memory for storing the decoded JPEG block. is there. When image information is transferred from the encoding device to the decoding device in the format shown in FIG. 3, the decoding side first decodes the run-length encoded data of the “01” raster unit, and starts the buffer memory 700. Store from. Next, JPEG data of the “01” raster unit is decoded, but the decoded image block cannot be immediately synthesized on the buffer memory 700. This is because when the run length data of the “02” raster unit is encoded using the upper reference, it is necessary to refer to the “01” raster unit before the JPEG block is synthesized. Therefore, since the JPEG block of the “01” raster unit needs to be synthesized after the run-length data of the “02” raster unit is decoded, the JPEG decoding buffer temporarily shown in FIG. It is necessary to store in the memory 701. To explain more clearly, an area where a pixel block determined to be subjected to JPEG coding has been replaced with a predetermined value, and run-length encoding may be performed with reference to the predetermined value. It is.
[0021]
When such a hybrid encoding method is applied to, for example, image information flowing between the host computer and the printer, the decoding device needs to be incorporated in the printer. Here, if the printer is an ink jet printer, the printable width is 20 cm, and the print resolution is 600 dpi, the JPEG decoding memory buffer shown in FIG. 7 will require approximately 111 KB. This is not applicable when there are few resources (memory) that the device can use.
[0022]
Further, according to FIG. 7, it is necessary to store the JPEG block output from the JPEG decoding module once in the buffer memory 701 and copy it to the buffer memory 700 for further synthesis. It can be a problem from a viewpoint.
[0023]
In the present embodiment, such problems are also eliminated. For this reason, the format forming unit 110 in FIG. 1 forms data in a format as shown in FIG.
[0024]
In the figure, a header part is generated at the head of the data series. This header portion includes information such as the size of the image to be compressed and encoded, the number of gradations per pixel, and how many lines each raster unit is composed of. Subsequently, two types of encoded image information are stored. As a feature of the present embodiment, only run-length data precedes other information by one raster unit. By forming the format in this way, the above problem can be solved. Note that the reason why only one raster unit precedes is when the pixel position to be referred to is within one raster unit when the pixel of interest is encoded.
[0025]
FIG. 9 shows the usage status of the memory inside the decoding apparatus according to this embodiment. The decoding procedure will be described below.
[0026]
The decoding device that has received the data series shown in FIG. 8 first analyzes the header part, and then decodes run-length data of the “01” raster unit. The decoded image is stored at the head of the buffer memory 900 shown in FIG. Next, the decoding apparatus decodes the run-length data of the subsequent “02” raster unit. At this time, the pixel of the “01” raster unit may be referenced (upward reference), but since no JPEG block is synthesized in the “01” raster unit, decoding can be performed without any problem. As a result, the obtained image information is stored in the composite image buffer memory following the decoded image information of the “01” raster unit. Next, the decoding device decodes the JPEG data of the subsequent “01” raster unit, and refers to the JPEG block position information of the “01” raster unit, while referring to the “01” raster unit portion of the composite image buffer in block units. I will synthesize with. In this way, JPEG block synthesis is always delayed by one raster unit with respect to decoding of run-length data. As a result, on the decoding side (the printer in the embodiment), the received JPEG data can be decoded and directly overwritten in the corresponding position of the buffer 900, and the JPEG decoding buffer memory conventionally required Is unnecessary or can be reduced. In particular, when a JPEG block is directly synthesized in the synthesized image buffer memory, a memory for storing JPEG encoded data of one pixel block is sufficient, and a separate buffer memory for JPEG decoding is not required. In addition, it is possible to dispense with copy processing from there.
[0027]
As can be seen from the above description, the decoding side (printer in the embodiment) receives the run-length encoded data received in advance by one raster unit, so basically, in the order received. For run-length encoded data, run-length decoding processing is performed, and for JPEG-encoded positions, it is only necessary to directly overwrite the corresponding positions in accordance with JPEG encoded data received thereafter. In other words, it can be said that the main part of the process, which is a feature of the above process, is on the encoding side.
[0028]
The processing on the encoding side can be realized by a computer program that runs on the host computer as described above. A specific configuration and processing procedure for realizing the above functions will be described below with reference to FIGS. In the following description, an example applied to a printer driver will be described.
[0029]
FIG. 13 is a block diagram of the host computer, and may be a general-purpose information processing apparatus such as a general personal computer. In the figure, reference numeral 1301 denotes a CPU that controls the entire apparatus, and reference numeral 1302 denotes a ROM that stores a boot program, BIOS, and the like. Reference numeral 1303 denotes a RAM used as a work area of the CPU 1301, and an OS, an application, and a printer driver are loaded and executed therein (for the run length buffer, JPEG buffer, and flag buffer shown in FIG. 14). (Clarified in the description of the flowchart). A hard disk 1304 stores an OS, applications, various data files, and a printer driver. Reference numeral 1305 denotes a keyboard and a pointing device (PD). 1306 has a built-in video memory. A display control unit 1307 draws an image to be displayed on the video memory and reads data from the video memory and outputs it as a video signal. A display device that displays an image according to a video signal. Reference numeral 1308 denotes an I / O interface for connection with a printer. When the printer exists on the network, this interface is a network interface.
[0030]
Now, in the above configuration, when an application is executed and print processing is performed, the printer driver generates a print image, performs compression encoding of the generated print image, and passes the result to the OS, so that I / Data in the format shown in FIG. 8 is output to the printer via the O interface 1308.
[0031]
FIG. 14 is a flowchart showing the procedure of the compression process of the printer driver. In starting the compression encoding process, a run-length buffer for temporarily storing run-length encoded data in the RAM 1303, a JPEG buffer for temporarily storing JPEG-compressed data, and a position A flag buffer for storing information (0 when the corresponding pixel block is run-length encoded, 1 when JPEG-encoded) is secured.
[0032]
In addition, it is sufficient to secure one raster unit for each run length buffer and two rasters for the flag buffer and the JPEG buffer. Also, the order of encoding for the raster of interest is one-dimensional. In the following description, flag (i, j) and the like are described as two-dimensional, but it should be noted that this is for convenience.
[0033]
First, in step S1401, a header part is generated and output. Next, variables i and j are both initialized to 1 in steps S1402 and S1403. The variable i stores information indicating the number of the raster unit, and the variable j stores information indicating the number of the pixel block in the raster unit.
[0034]
In step S1404, (i, j) in the flag buffer is initialized to zero. In short, since the position of the pixel block of interest can be expressed as (i, j), this means that the pixel block is set to be run-length encoded.
[0035]
In step S1405, it is determined whether the pixel block of interest should be JPEG encoded or run-length encoded. This determination is made as described above, and a detailed description thereof is omitted here.
[0036]
If it is determined that JPEG encoding should be performed, the process proceeds to step S1406, flag (i, j) is reset to 1, and JPEG compression encoding is performed in step S1407. The generated encoded data is stored (accumulated) in the JPEG buffer. As a result, since the region of the target pixel block in the original image has been used, the values of RGB are filled with predetermined values (255 in the embodiment) (step S1408).
[0037]
Thereafter, the process proceeds to step S1409, and line length encoding is performed on the target pixel block. The point to be noted here is that there are two types of processing in step S1409, that is, a case where it is determined No in step S1405 and a case where processing is performed after step S1408. In the latter case, since all the pixel values in the pixel block are uniformly the same value, the encoding efficiency of run-length encoding is maximized.
[0038]
When the process proceeds to step S1409, whether or not the position of the pixel block of interest is at the end position of the raster unit is determined by examining the variable j. If it is determined that the process is in progress, the process proceeds to step S1411, where the variable j is incremented by one to perform the process for the pixel block at the next position, and the process returns to step S1404.
[0039]
If it is determined in step S1410 that the encoding process for one raster unit has been completed, the process proceeds to step S1412, and the run-length buffer stores run-length encoded data for one raster unit. Therefore, the code data is output.
[0040]
When the process proceeds to step S1413, it is determined whether or not the variable i is 1, that is, whether or not the encoding process of the first raster unit is performed. In the case of the data of the first raster unit, only run-length encoded data is output as shown in FIG. 8, so the process proceeds to step S1416, and the variable i is set to 1 in order to encode the next raster unit. Increment and return to step S1403. At this time, it should be noted that the flag buffer and the JPEG buffer store data corresponding to the previous time, that is, the (i−1) th raster unit.
[0041]
When the second and subsequent raster units are encoded as described above and the output processing of the run-length encoded data is completed, i is other than 1 in the determination process in step S1413, and the process proceeds to step S1414. . When the process proceeds to step S1414, the output of the i-1th run-length encoded data and the i-1th JPEG encoded data are output after the output of the i-th runlength encoded data in step S1412. Will be output.
[0042]
When the process proceeds to step S1415, the variable i is checked to determine whether or not the process for the final raster unit has been completed. If not, the process returns to step S1403 via step S1416.
[0043]
If it is determined in step S1415 that the variable i indicates the final raster, the i-th data remains in the flag buffer and JPEG buffer in an unoutput state, so that the output processing is performed in step S1417. This process is terminated.
[0044]
As a result, print data according to the data format shown in FIG. 8 is output. Note that run-length encoding may be performed in units of raster units rather than in units of pixel blocks. In this case, the process of step S1409 may be performed immediately after step S1401.
[0045]
<Second Embodiment>
In the first embodiment, since a JPEG processing unit is an 8-pixel square block, one raster unit is composed of 8 lines. On the other hand, in the second embodiment, as shown in FIG. 10, a data sequence generation method in the case where one raster unit is composed of 8 × 3 = 24 lines will be described. That is, this is a case where the recording head has 24 vertical nozzles. In addition, suppose that 8 lines which comprised one raster unit in 1st Embodiment are called a band in this embodiment.
[0046]
In the second embodiment, it is assumed that the position of the upper reference pixel in the run-length encoding shown in FIG. 6 is not separated from the target pixel by 8 pixels or more. In this case, in order to correctly decode the 01 band of the “02” raster unit shown in FIG. 10, the JPEG block is not synthesized on the “03” band of the “01” raster unit at the time of decoding. Become. Therefore, in the second embodiment, a data series as shown in FIG. 11 is generated in the format forming unit 110 of FIG. In the data series of FIG. 11, as in the first embodiment, a header portion is present at the head, followed by run-length data from “01” band to “03” band of the “01” raster unit. In the figure, (01RU: 01B) to (01RU: 03B) mean the “01” band to the “03” band of the “01” raster unit.
[0047]
Further, in the format of FIG. 11, the JPEG block position information and JPEG data from (01RU: 01B) to (01RU: 02B) are continued. That is, the (01RU: 03B) JPEG block position information and JPEG data are not included here. Next, run length data from (02RU: 01B) to (02RU: 03B) follows, followed by JPEG block position information and JPEG data from (01RU: 03B) to (02RU: 02B). That is, the format is formed by delaying the JPEG block position information and JPEG data by one band with respect to the run-length data.
[0048]
The decoding apparatus that receives the data series shown in FIG. 11 first analyzes the header part and then decodes run length data from (01RU: 01B) to (01RU: 03B). The image information obtained as a result of decoding is stored in the head portion of the composite image buffer memory 1200 shown in FIG. Next, the JPEG data from (01RU: 01B) to (01RU: 02B) is decoded and synthesized in a block unit at a predetermined position in the synthesized image buffer memory 1200 while referring to the JPEG block position information. FIG. 12 shows the memory usage status when the decoding is completed so far.
[0049]
Next, the decoding apparatus decodes the run length data from (02RU: 01B) to (02RU: 03B), and stores the resulting image information at the head of the unused area of the buffer memory 1200. At this time, since no JPEG block is synthesized in (01RU: 03B), the run-length data in (02RU: 01B) can be decoded without any problem.
[0050]
Next, the decoding apparatus decodes the JPEG data from (01RU: 03B) to (02RU: 02B), and synthesizes the data at a predetermined position on the buffer memory 1200 while referring to the JPEG block position information.
[0051]
As described above, by generating a data sequence in the format as shown in FIG. 11, it is possible to decode image information without a JPEG decoding buffer memory that is conventionally required in a decoding apparatus. It becomes. In addition, the above processing eliminates the need for JPEG block copy processing from the JPEG decoding buffer to the composite image buffer, which has been conventionally required. This completes the description of the second embodiment.
[0052]
Also in the second embodiment, the decoding side (the printer in the embodiment) performs decoding processing based on the received run-length encoded data, and the JPEG encoded position is decoded according to the JPEG encoded data. It can be said that the main part is on the encoding side.
[0053]
The processing procedure on the encoding side in the second embodiment is substantially the same as that of the first embodiment described above except that one raster unit is composed of a plurality of bands. From this flowchart, it will be obvious to those skilled in the art, and the description thereof will be omitted.
[0054]
As described above, as is clear from the description in the present embodiment, the main part of the feature of the present invention is on the side for compressing and encoding image data. As described above, since the compression encoding is realized by a computer program such as a printer driver, it is obvious that the present invention also includes a computer program. In general, a computer program can be executed by setting a computer readable storage medium such as a CDROM in a computer and copying or installing the computer program in a system. It is also clear to do.
[0055]
Furthermore, the computer program for realizing the above processing is based on the instructions of the program, and an operating system (OS) operating on the computer performs part or all of the actual processing, and the processing Needless to say, the case where the functions of the above-described embodiment are realized is also included.
[0056]
As described above, according to the first embodiment, JPEG block synthesis is performed by always delaying one raster unit with respect to decoding of run-length data, so that the JPEG decoding buffer memory It becomes unnecessary or can be reduced. Further, since the JPEG block can be directly synthesized in the synthesized image buffer memory, the copy processing from the JPEG decoding buffer memory can be made unnecessary.
[0057]
Further, according to the second embodiment, by generating a data sequence in a format as shown in FIG. 11, it becomes possible to decode image information without a JPEG decoding buffer memory. It is also possible to achieve the same effect as the embodiment.
[0058]
In the embodiment, run length coding and JPEG coding have been described as examples of coding types. However, the present invention is not limited by this, and the coding unit is also limited to 8 × 8 pixels. is not. In short, what is necessary is just to use two types of lossless encoding such as run-length encoding and irreversible encoding such as JPEG.
[0059]
As described above, the embodiments corresponding to the present embodiment are listed as follows.
[0060]
[Embodiment 1] An image processing method for encoding image data in units of pixel blocks of a predetermined size,
A first encoding step of irreversibly encoding image data;
A second encoding step for lossless encoding of the image data;
A step of determining whether or not to perform the first encoding step for each pixel block of the image data;
A first accumulating step for temporarily accumulating code data of pixel blocks obtained by encoding in the first encoding step when it is determined in the determining step that encoding is performed in the first encoding step; ,
A replacement step of replacing all pixel values in the pixel block to be encoded in the first encoding step with a predetermined value;
The pixel block after replacement in the replacement step and the pixel block determined not to be performed in the first encoding step in the determination step are encoded in the second encoding step, and obtained. A second accumulation step for temporarily accumulating the encoded data;
An output step of outputting the encoded data accumulated in the first accumulation step with a delay by a predetermined unit from the encoded data accumulated in the second accumulation step;
An image processing method comprising:
[0061]
[Embodiment 2] The embodiment according to Embodiment 1, wherein the predetermined unit has a distance that is a distance between a position of a pixel to be encoded in the first encoding step and a pixel position to be referred to. Image processing method.
[0062]
[Embodiment 3] Embodiment 1 or 2, wherein the first encoding step is an encoding step by JPEG encoding, and the second encoding step is an encoding step by a run-length encoding step. An image processing method described in 1.
[0063]
[Embodiment 4] The image processing method according to any one of Embodiments 1 to 3, wherein an output destination in the output step is a printing apparatus.
[0064]
[Embodiment 5] An image processing apparatus for encoding image data in units of pixel blocks of a predetermined size,
First encoding means for irreversibly encoding image data;
A second encoding means for losslessly encoding image data;
A determination unit that determines whether or not to perform the first encoding unit for each pixel block of the image data;
A first accumulator that temporarily accumulates code data of a pixel block obtained by encoding by the first encoder when the determination unit determines that the first encoder encodes; ,
Replacement means for replacing all pixel values in the pixel block to be encoded by the first encoding means with a predetermined value;
The pixel block after replacement by the replacement unit and the pixel block determined not to be performed by the first encoding unit by the determination unit are encoded by the second encoding unit. Second storage means for temporarily storing the encoded data,
Output means for outputting the encoded data stored in the first storage means with a predetermined unit delay from the encoded data stored in the second storage means;
An image processing apparatus comprising:
[0065]
[Embodiment 6] A computer program that functions as an image processing apparatus that encodes image data in units of pixel blocks of a predetermined size,
First encoding means for irreversibly encoding image data;
A second encoding means for losslessly encoding image data;
A determination unit that determines whether or not to perform the first encoding unit for each pixel block of the image data;
A first accumulator that temporarily accumulates code data of a pixel block obtained by encoding by the first encoder when the determination unit determines that the first encoder encodes; ,
Replacement means for replacing all pixel values in the pixel block to be encoded by the first encoding means with a predetermined value;
The pixel block after replacement by the replacement unit and the pixel block determined not to be performed by the first encoding unit by the determination unit are encoded by the second encoding unit. Second storage means for temporarily storing the encoded data,
Output means for outputting the encoded data stored in the first storage means with a predetermined unit delay from the encoded data stored in the second storage means;
A computer program that functions as a computer program.
[0066]
[Embodiment 7] The computer program according to Embodiment 6, wherein the computer program is a part of a printer driver.
[0067]
[Embodiment 8] A computer-readable storage medium storing the computer program according to Embodiment 6 or 7.
[0068]
【The invention's effect】
As described above, according to the present invention, it is possible to reduce the amount of memory required for decoding encoded image data in which lossless encoded data and lossy encoded data are mixed.
[Brief description of the drawings]
FIG. 1 is a block configuration diagram of an encoding process in an embodiment.
FIG. 2 is a conceptual diagram of plane division in the embodiment.
FIG. 3 is a diagram showing a data format to be a problem.
FIG. 4 is a hardware configuration diagram of a printer according to the embodiment.
FIG. 5 is a functional block diagram relating to a decoding process in the configuration of FIG. 4;
FIG. 6 is a diagram illustrating reference positions for run-length encoding.
7 is a diagram showing a memory usage state in the decoding device at the time of the data format of FIG. 3; FIG.
FIG. 8 is a diagram showing a data format in the first embodiment.
FIG. 9 is a diagram illustrating an example of memory use inside the decoding device according to the first embodiment;
FIG. 10 is a diagram for explaining a raster unit according to a second embodiment.
FIG. 11 is a diagram showing a data format in the second embodiment.
FIG. 12 is a diagram illustrating an example of memory use in the decoding device according to the second embodiment.
FIG. 13 is a hardware configuration diagram of a host computer in the first embodiment.
FIG. 14 is a flowchart illustrating an encoding processing procedure according to the first embodiment.

Claims (8)

An image processing method for encoding image data in units of pixel blocks,
A first encoding step of encoding the image data with a first encoding algorithm;
A step of determining whether or not to perform the first encoding step for each pixel block of the image data;
A first accumulating step of temporarily accumulating encoded data of the pixel block obtained by encoding in the first encoding step when it is determined in the determining step that encoding is performed in the first encoding step; When,
A replacement step of replacing all pixel values in the pixel block to be encoded in the first encoding step with a preset value;
A second encoding step of encoding the pixel block after the replacement and a pixel block determined not to be performed in the first encoding step in the determination step with a second encoding algorithm;
An output step of outputting the encoded data stored in the first storage step after being delayed by a preset unit from the encoded data obtained by encoding in the second encoding step. An image processing method.   The image processing method according to claim 1, wherein the second encoding step is a step of performing encoding by referring to surrounding pixels.   The image according to claim 1 or 2, wherein the first encoding step is an encoding step by lossy encoding, and the second encoding step is an encoding step by lossless encoding. Processing method.   The image processing method according to claim 1, wherein an output destination in the output step is a printing apparatus. An image processing apparatus that encodes image data in units of pixel blocks,
First encoding means for encoding image data with a first encoding algorithm;
A determination unit that determines whether or not to perform the first encoding unit for each pixel block of the image data;
First storage means for temporarily storing the encoded data of the pixel block obtained by encoding by the first encoding means when the determination means determines that the encoding is performed by the first encoding means. When,
Replacement means for replacing all pixel values in a pixel block to be encoded by the first encoding means with a preset value;
A second encoding unit that encodes the pixel block after the replacement, and a pixel block determined not to be performed by the first encoding unit by the determination unit using a second encoding algorithm;
Output means for outputting the encoded data accumulated by the first accumulating means after being delayed by a preset unit from the encoded data obtained by encoding by the second encoding means. An image processing apparatus. A computer program that functions as an image processing device that encodes image data in units of pixel blocks of a preset size by being read and executed by a computer,
First encoding means for encoding image data with a first encoding algorithm;
A determination unit that determines whether or not to perform the first encoding unit for each pixel block of the image data;
First storage means for temporarily storing the encoded data of the pixel block obtained by encoding by the first encoding means when the determination means determines that the encoding is performed by the first encoding means. When,
Replacement means for replacing all pixel values in a pixel block to be encoded by the first encoding means with a preset value;
A second encoding unit that encodes the pixel block after the replacement, and a pixel block determined not to be performed by the first encoding unit by the determination unit using a second encoding algorithm;
Output means for outputting the encoded data stored in the first storage means after being delayed by a preset unit from the encoded data obtained by encoding in the second encoding means. A computer program characterized by functioning.   The computer program according to claim 6, wherein the computer program is a part of a printer driver.   A computer-readable storage medium storing the computer program according to claim 6 or 7.

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