JP2011023926A - Image compression apparatus, imaging apparatus, program and image decompression apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a means for performing compression/decompression of an image without referring to an LUT. <P>SOLUTION: This image compression apparatus includes: a difference calculation part which obtains predicted difference of pixels of an image to be processed; an encoding processing part which obtains a predetermined value by size of the predicted difference of the pixels, and obtains a first variable-length code showing a remainder obtained by dividing an absolute value of the predicted difference by the predetermined value, a second variable-length code showing a quotient obtained by dividing the absolute value of the predicted difference by the predetermined value, and a third fixed-length code showing positive and negative of the predicted difference; and a compression information generation part which arranges the first code, the second code, and the third code in a predetermined order to generate compression information of the image to be processed. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to an image compression apparatus, an imaging apparatus, a program, and an image expansion apparatus.

  Conventionally, as shown in Patent Document 1 as an example, in digital image compression processing, a method of performing Huffman coding after replacing pixel values of an image with adjacent pixel differences, DCT coefficients, or the like is known. Note that in the case of image compression / decompression processing by Huffman coding, an LUT (Huffman table) indicating the correspondence between codes before and after compression is generally required.

JP 2000-244744 A

  However, in the conventional technique, there is still room for improvement in that the function of referring to the LUT is required in the image compression / decompression processing, which is costly.

  Therefore, an object of the present invention is to provide a means for compressing / decompressing an image without referring to an LUT.

  An image compression apparatus according to an aspect includes a difference calculation unit that calculates a prediction difference of a pixel of a processing target image, a predetermined value based on a size of the prediction difference of the pixel, and an absolute value of the prediction difference divided by the predetermined value A code for obtaining a variable-length first code indicating the remainder, a variable-length second code indicating the quotient obtained by dividing the absolute value of the prediction difference by a predetermined value, and a fixed-length third code indicating whether the prediction difference is positive or negative And a compression information generation unit that arranges the first code, the second code, and the third code in a predetermined order to generate compression information of the processing target image.

In the image compression apparatus according to one aspect, the encoding processing unit may obtain the encoding number n based on the size of the pixel prediction difference and set 2 ⁿ as a predetermined value. The compressed information generation unit may associate pixel information in which the first code, the second code, and the third code are arranged in a predetermined order with the encoding number n. Further, the image processing apparatus further includes a region dividing unit that divides the processing target image into a plurality of regions, and the encoding processing unit encodes an encoding number for each region based on an average absolute value of prediction differences of a plurality of pixels in the region. n may be obtained. Further, the image processing apparatus further includes a region dividing unit that divides the processing target image into a plurality of regions, and the encoding processing unit encodes an encoding number for each region based on an average absolute value of prediction differences of a plurality of pixels in the region. n may be obtained. For example, when the average value of the absolute values of the prediction differences is M, the encoding processing unit sets a variable N that is an integer of 0 or more that minimizes the value of “((M + 0.5) / 2 ^N ) + N”. May be the encoding number n.

In one aspect, the encoding processing unit continues one binary code up to a quotient value obtained by dividing the absolute value of the prediction difference by 2 ⁿ , and adds the other binary code to the end of one code. The second code may be generated by attaching.

  An image pickup apparatus including an image compression apparatus according to one aspect, a program that causes a computer to operate as an image compression apparatus according to one aspect, a storage medium that stores the program, and an operation of the image compression apparatus according to one aspect Those expressed in the above category are also effective as specific embodiments of the present invention.

  Furthermore, an image expansion device that expands the compression information of the processing target image generated by the image compression device of one aspect, a program that causes a computer to operate as the image expansion device, a storage medium that stores the program, A representation of the operation of the image expansion apparatus in the method category is also effective as a specific aspect of the present invention.

  In the present invention, the first code, the second code, and the third code are arranged in a predetermined order and the compression information of the processing target image is generated, so that the image can be compressed / decompressed without referring to the LUT.

1 is a block diagram showing a configuration example of an image processing apparatus according to a first embodiment. A flowchart for explaining an operation example of image compression processing in the first embodiment The figure which shows the example of a calculation of the prediction difference in a picture in 1st Embodiment. Schematic diagram showing an example of the data structure of the compressed file of the image to be processed A plot of the relationship between the absolute value of the value to be encoded and the code length when compressed FIG. 5 is a diagram in which a straight line of the approximate expression of Expression (3) is added. A flowchart for explaining an operation example of image decompression processing in the first embodiment The block diagram which shows the structural example of the electronic camera in 2nd Embodiment.

<Description of First Embodiment>
FIG. 1 is a block diagram illustrating a configuration example of an image processing apparatus according to the first embodiment. The image processing apparatus according to one embodiment is a personal computer in which a program is installed. The computer 11 constituting the image processing apparatus performs compression processing on a digital image to be processed (processing target image) by executing a program. The computer 11 can also decompress the compression information (compressed file described later) of the processing target image generated by the compression process by executing the program.

  Here, the processing target image may be an image obtained by imaging a subject with an imaging device such as an electronic camera or a scanner, or may be an image drawn on the computer 11.

  A computer 11 illustrated in FIG. 1 includes a data reading unit 12, a storage device 13, a CPU 14, a memory 15, an input / output I / F 16, and a bus 17. The data reading unit 12, the storage device 13, the CPU 14, the memory 15, and the input / output I / F 16 are connected to each other via a bus 17. Further, an input device 18 (keyboard, pointing device, etc.) and a monitor 19 are connected to the computer 11 via an input / output I / F 16. The input / output I / F 16 receives various inputs from the input device 18 and outputs display data to the monitor 19.

  The data reading unit 12 is used when reading the processing target image or the program from the outside. For example, the data reading unit 12 communicates with a reading device (such as an optical disk, a magnetic disk, or a magneto-optical disk reading device) that acquires data from a removable storage medium, or an external device in accordance with a known communication standard. It consists of communication devices (USB interface, LAN module, wireless LAN module, etc.) to be performed.

  The storage device 13 is configured by a storage medium such as a hard disk or a nonvolatile semiconductor memory. The storage device 13 stores the above program and various data necessary for executing the program. Note that the storage device 13 can also store information on the processing target image read from the data reading unit 12, compression information (a compressed file described later) of the processing target image, and the like.

  The CPU 14 is a processor that comprehensively controls each unit of the computer 11. The CPU 14 functions as a difference calculation unit 21, a region division unit 22, a number acquisition unit 23, an encoding processing unit 24, and a compression information generation unit 25 by executing the program (in addition, each unit included in the CPU 14). Will be described later).

  The memory 15 temporarily stores the calculation result of the program. The memory 15 is composed of, for example, a volatile SDRAM.

(Operation example of image compression processing)
Next, an operation example of image compression processing by the image processing apparatus according to the first embodiment will be described with reference to the flowchart of FIG. The processing in FIG. 2 is started when the CPU 14 executes a program in response to a program execution instruction from the user.

  Step S101: The CPU 14 acquires a processing target image from the data reading unit 12 or the storage device 13. In the first embodiment, for the sake of simplicity, an example will be described in which a grayscale image that does not include color information is a processing target image.

  Step S102: The difference calculation unit 21 obtains an intra-image prediction difference at each pixel of the processing target image. For example, the difference calculation unit 21 may obtain a pixel value difference with an adjacent pixel or a pixel value difference with a pixel several pixels away from each pixel as an intra-picture prediction difference by a known method. The difference calculation unit 21 analyzes the processing target image to obtain an image structure (correlation of pixel values in the image), and obtains a pixel difference in a direction in which the correlation of pixel values increases for each pixel. May be.

  As an example, FIG. 3 shows a calculation example of the intra-picture prediction difference in the first embodiment. The difference calculation unit 21 in the example of FIG. 3 sets the difference in pixel value from the pixel adjacent to the left side in the top row of the processing target image as the intra-picture prediction difference of the pixel. Note that the difference calculation unit 21 uses the pixel value of the pixel in the upper left corner of the processing target image as it is. Moreover, the difference calculation part 21 makes the difference of a pixel value with the pixel adjacent on the upper side the prediction difference in a pixel of a pixel in other lines except the uppermost line of a process target image.

  Step S103: The area dividing unit 22 performs an area dividing process for dividing the processing target image into a plurality of areas. As an example, the area dividing unit 22 divides the processing target image into a grid pattern by blocks of 4 × 4 pixel size.

  Step S104: The number acquisition unit 23 obtains an encoding number n based on the size of the intra-picture prediction difference in each block in each block (S103).

  As an example, the number acquisition unit 23 obtains the average value M of the absolute values of intra-picture prediction differences in each block in each block. Next, the number acquisition unit 23 obtains the value of the variable N that minimizes the value (predicted code length) according to the following equation (1) for each block. Note that the predicted code length of Equation (1) corresponds to the average code length of the pixels in the block. The number acquisition unit 23 sets the variable N as the encoding number n in each block (N = n).

  However, in the formula (1), the variable N is an integer of 0 or more. In the example of the first embodiment, the variable N is limited to a range of 1-8.

  Step S105: The CPU 14 designates a block B to be encoded from among a plurality of blocks included in the processing target image. As an example, when changing the position of the block B to be encoded, the CPU 14 in S105 shifts the block B by sequentially scanning from left to right one row at a time starting from the upper left corner of the processing target image. .

  Step S106: The CPU 14 designates the pixel P to be encoded from the block B (S105) to be encoded. As an example, when changing the position of the pixel P to be encoded, the CPU 14 in S106 shifts the pixel P by sequentially scanning from left to right one row at a time from the upper left corner of the block B.

  Step S107: The encoding processing unit 24 performs an encoding process according to the following rule using the value of the encoding number n corresponding to the block B to which the pixel P belongs.

<< When n is other than the maximum value (1-7 in the first embodiment) >>
(A) First, the encoding processing unit 24 obtains a remainder obtained by dividing the absolute value of the intra-picture prediction difference of the pixel P by 2 ⁿ . Then, the encoding processing unit 24 generates a variable-length first code by binary encoding the obtained remainder value. In this case, the remainder value is in the range of 0 to 2 ⁿ −1 and can be expressed by n bits. Therefore, the code length of the first code can be uniquely determined by the number of bits corresponding to the value of the encoding number n corresponding to the pixel P.

(B) Secondly, the encoding processing unit 24 obtains a quotient obtained by dividing the absolute value of the intra-picture prediction difference of the pixel P by 2 ⁿ . Then, the encoding processing unit 24 continues the binary “1” code up to the obtained quotient value, and adds a binary “0” code indicating the end to the end of the variable length second. Generate a code. The encoding processing unit 24 may generate the second code by inverting the above “0” and “1”.

  (C) Thirdly, the encoding processing unit 24 generates a third code having a 1-bit fixed length indicating whether the intra prediction prediction difference of the pixel P is positive or negative. For example, the encoding processing unit 24 sets the third code to “0” if the intra-picture prediction difference of the pixel P is positive, and sets the third code to “1” if the intra-picture prediction difference of the pixel P is negative. To do. When the intra-picture prediction difference of the pixel P is “0”, the encoding processing unit 24 omits the generation of the third code.

  (D) And the encoding process part 24 produces | generates the pixel information of the pixel P which has arrange | positioned said 1st code | symbol, 2nd code | symbol, and 3rd code | symbol in predetermined order. For example, the encoding processing unit 24 in the first embodiment generates pixel information by connecting the codes in the order of the first code, the second code, and the third code (see FIG. 4). Of course, the encoding processing unit 24 may appropriately change the arrangement order of the first code, the second code, and the third code in the pixel information.

  Here, an example of generating pixel information in the above case will be described. As an example, let us consider a case where the intra-picture prediction difference of the pixel P is −29 and the encoding number n is 3.

In this case, the remainder obtained by dividing the absolute value (29) of the intra-picture prediction difference by 2 ³ (8) is 5, and the first code is “101” in binary 3 bits. Further, since the quotient obtained by dividing the absolute value (29) of the intra-picture prediction difference by 2 ³ (8) is 3, the second code is “1110”. Further, since the intra-picture prediction difference is a negative value, the third code is “1”. Therefore, the pixel information in the above case is “10111101”. If the arrangement order of the first code to the third code and the encoding number n are known, the upper n bits of the pixel information can be identified as the first code. Similarly, the second code included in the pixel information can be identified by the code “0” indicating the end.

  As another example, consider a case where the intra-picture prediction difference of the pixel P is “0” and the encoding number n is 3.

In this case, the remainder obtained by dividing the absolute value (0) of the intra-picture prediction difference by 2 ³ (8) is 0, and the first code is “000” in binary 3 bits. Further, since the quotient obtained by dividing the absolute value (0) of the intra-picture prediction difference by 2 ³ (8) is also 0, the second code is only “0” indicating the end. In addition, since the intra-picture prediction difference is 0, the third code is omitted. Therefore, the pixel information in the above case is “0000”. Thus, when “0” follows immediately after the first code (upper n bits) of the pixel information, it can be determined that the absolute value of the intra-picture prediction difference is “0”. It is possible to identify the pixel information.

<< When n is the maximum value (8 in the first embodiment) >>
In this case, the encoding processing unit 24 performs binary encoding on the absolute value of the intra-picture prediction difference of the pixel P instead of the processes (A) and (B). And the encoding process part 24 produces | generates the pixel information of the pixel P by giving the 3rd code | symbol of 1 bit fixed length which shows the positive / negative of the prediction difference in the image of the pixel P to the end similarly to said (C). .

  Step S108: The CPU 14 determines whether or not the current pixel P is the last pixel of the block B (pixel at the lower right corner of the block B). If the above requirement is satisfied (YES side), the process proceeds to S109. In this case, pixel information is generated in all the pixels of the block B.

  On the other hand, if the above requirement is not satisfied (NO side), the CPU 14 returns to S106 to re-specify the pixel P and repeat the above operation. Note that pixel information of each pixel included in the block B is sequentially generated by the NO-side loop in S108.

  Step S109: The compression information generation unit 25 associates the pixel information of each pixel of the block B with the encoding number n of the block B, and generates the compression information of the block B.

  As an example, the compression information generation unit 25 in S109 records the encoding number n in the predetermined number of bits (3 bits) at the head of the compression information. Then, the compression information generation unit 25 records pixel information for 16 pixels in accordance with the designation order of the pixels P (see FIG. 4). If the position and the number of bits of the code indicating the encoding number n and the number of pieces of pixel information for one block are known, each piece of information included in the compressed information can be identified.

  Step S110: The CPU 14 determines whether or not the current block B is the last block (the block at the lower right corner of the processing target image). If the above requirement is satisfied (YES side), the process proceeds to S111. In this case, compression information is generated in all blocks of the processing target image.

  On the other hand, if the above requirement is not satisfied (NO side), the CPU 14 returns to S105, redesignates the block B, and repeats the above operation. Note that the compression information of each block included in the processing target image is sequentially generated by the NO-side loop in S110.

  Step S111: The compression information generation unit 25 generates a compressed file of the processing target image by associating the header information with the compression information of each block. Then, the CPU 14 records the compressed file in the storage device 13.

  As an example, FIG. 4 schematically shows the data structure of the compressed file of the processing target image. Header information is recorded at the head of the compressed file, and the compressed information of each block is recorded after the header information in accordance with the designation order of block B.

  The header information includes, for example, image size information (number of vertical and horizontal pixels) of a processing target image, size information of one block (number of vertical and horizontal pixels), block arrangement information (number of vertical and horizontal blocks), and encoding number. Information on the number of recording bits of n is included. The header information is generated by the compressed information generation unit 25. Above, description of the flowchart of FIG. 2 is complete | finished.

  The image compression apparatus according to the first embodiment encodes each pixel based on an encoding number n. Therefore, unlike Huffman coding, an image can be coded without referring to the LUT.

  Also in the encoding of the first embodiment, a small value becomes a short code as in the Huffman encoding. In general, since the adjacent pixel difference of an image has a high probability of being a small value, the code after compression tends to be shorter on average. Therefore, the image compression apparatus of the first embodiment can efficiently compress image information.

  By the way, when different encoding is performed for each region in Huffman encoding, a different LUT is required for each region, and it is relatively difficult to perform different encoding processing for each region. On the other hand, the image compression apparatus according to the first embodiment can very easily execute different encoding processes for each region by changing the encoding number n in each block. In addition, when the inventor conducted an experiment, the image compression apparatus according to the first embodiment compresses an image by changing the encoding number n for each block, rather than compressing the entire image by the same Huffman encoding process. Was able to obtain a high compression ratio. In the first embodiment, if the encoding number n is set small, encoding of a small value is advantageous, and if the encoding number n is set large, encoding of a large value is advantageous.

  In addition, the image compression apparatus according to the first embodiment can easily obtain the encoding number n with very high compression efficiency for each block by the above equation (1). Here, in the first embodiment, the code length obtained by encoding from the value to be encoded for one pixel (adjacent pixel difference) can be obtained by the following equation (2).

  “INT (x)” in Expression (2) indicates a function that returns the maximum integer not exceeding x. Further, in the first embodiment, when the value to be encoded is 0, the positive and negative codes (third code) are omitted, so that the code length is actually shorter by one bit than the calculation result of Expression (2). FIG. 5 is a diagram in which the relationship between the absolute value of the value to be encoded (adjacent pixel difference) and the code length at the time of compression is plotted using the expression (2) in the encoding numbers 1-4.

  The code length of the above equation (2) can be approximately obtained by the following equation (3). FIG. 6 is a diagram in which a straight line of the approximate expression of Expression (3) is added to FIG. According to FIG. 6, it can be seen that the calculation result of Expression (3) closely approximates the calculation result of Expression (2).

  In addition, since said Formula (3) is a linear formula, said "code length" is made into the average (predicted code length) of several code length, said above "absolute value of the value to encode" It is also possible to replace the average of the absolute values of a plurality of values to be encoded, thereby obtaining the above equation (1). From the above description, it can be seen that the encoding number n obtained by the above equation (1) can minimize the average code length in each block.

(Example of image expansion processing)
Next, an operation example of image decompression processing by the image processing apparatus according to the first embodiment will be described with reference to the flowchart of FIG. The process of FIG. 7 is started when the CPU 14 executes a program in response to a program execution instruction from the user.

  Step S201: The CPU 14 acquires a compressed file of the processing target image (generated in S111 above) from the data reading unit 12 or the storage device 13.

  Step S202: The CPU 14 refers to the header information included in the compressed file, and acquires the image size information of the processing target image, the size information of one block, the arrangement information of the block, and the number of recording bits of the encoding number n.

  Step S203: The CPU 14 sequentially decompresses the compression information of each block included in the compressed file.

  Specifically, the CPU 14 acquires the encoding number n corresponding to the block from the head of the compression information of each block based on the information on the number of recording bits of the encoding number n. Next, the CPU 14 sequentially expands each piece of pixel information in the block based on the above-described encoding rule of S107, and acquires the value of the intra-picture prediction difference of each pixel. Note that the CPU 14 can correctly rearrange the values of the intra-picture prediction differences of each pixel by referring to the size information of one block.

  And CPU14 can acquire the value of the prediction difference in a picture in all the pixels of a process target picture by repeating said operation | movement by each block. The CPU 14 can correctly rearrange each block by referring to the image size information of the processing target image or the block arrangement information.

  Step S204: The CPU 14 obtains each pixel value of the processing target image from the value of the intra-picture prediction difference acquired in S203. Thereby, the CPU 14 can restore the processing target image from the compressed file. The CPU 14 may display and output the restored processing target image on the monitor 19, or may record the restored processing target image in the storage device 13.

<Description of Second Embodiment>
FIG. 8 is a block diagram illustrating a configuration example of the electronic camera according to the second embodiment. The electronic camera 31 includes an imaging optical system 32, an imaging element 33, an image processing engine 34, a ROM 35, a main memory 36, a recording I / F 37, and an operation unit 38 that receives user operations. . Here, the image sensor 33, the ROM 35, the main memory 36, the recording I / F 37, and the operation unit 38 are connected to the image processing engine 34, respectively.

  The imaging element 33 is an imaging device that captures an image of a subject formed by the imaging optical system 32 and generates an image signal of the captured image. The image signal output from the image sensor 33 is input to the control unit via an A / D conversion circuit (not shown).

  The image processing engine 34 is a processor that comprehensively controls the operation of the electronic camera 31. For example, the image processing engine 34 performs various types of image processing (color interpolation processing, gradation conversion processing, contour enhancement processing, white balance adjustment, color conversion processing, etc.) on the captured image data. Further, the image processing engine 34 is configured as an image compression device (difference calculation unit 21, area division unit 22, number acquisition unit 23, encoding processing unit 24, and compression information generation unit 25 of the first embodiment) by executing a program. Function.

  The ROM 35 stores a program executed by the image processing engine 34. The main memory 36 temporarily stores image data in the pre-process and post-process of image processing.

  The recording I / F 37 has a connector for connecting a nonvolatile storage medium 39. The recording I / F 37 executes data writing / reading with respect to the storage medium 39 connected to the connector. The storage medium 39 includes a hard disk, a memory card incorporating a semiconductor memory, or the like. In FIG. 8, a memory card is illustrated as an example of the storage medium 39.

  The electronic camera 31 according to the second embodiment performs the image compression process according to the first embodiment (the process illustrated in the flowchart of FIG. 2) on the image captured by the image sensor 33 in the imaging process triggered by the user's imaging instruction. Apply. Then, the electronic camera 31 records the compressed file of the captured image on the storage medium 39. As a result, the electronic camera 31 of the second embodiment can efficiently record more image information on the storage medium 39.

<Supplementary items of the embodiment>
In each of the above embodiments, an example has been described in which the functions of the difference calculation unit 21, the region division unit 22, the number acquisition unit 23, the encoding processing unit 24, and the compression information generation unit 25 are realized by software. Of course, the above-described units may be realized by hardware using an ASIC.

  In the first embodiment described above, an example in which a grayscale image is a processing target image has been described. However, a color image may be subjected to the image compression processing of the present invention as a matter of course. For example, when the image compression processing of the present invention is performed on a color image, the above-described image compression processing may be executed for each of the RGB channels. Alternatively, the above-described image compression processing may be executed on each YCbCr channel.

  In the first embodiment, the range of the encoding number n (1-8) and the size of one block (4 × 4 pixels) are merely examples, and these parameters are appropriately changed when the present invention is implemented. May be.

  In the first embodiment, when the size of one block and the number of recording bits of the encoding number n are standardized and uniquely determined, the above information may be omitted from the header information. .

  Note that the imaging device of the present invention can be widely applied to imaging devices such as camera modules incorporated in electronic devices such as mobile phones, single-lens reflex electronic cameras, and scanners.

  From the above detailed description, features and advantages of the embodiments will become apparent. It is intended that the scope of the claims extend to the features and advantages of the embodiments as described above without departing from the spirit and scope of the right. Further, any person having ordinary knowledge in the technical field should be able to easily come up with any improvements and modifications, and there is no intention to limit the scope of the embodiments having the inventive features to those described above. It is also possible to use appropriate improvements and equivalents within the scope disclosed in.

DESCRIPTION OF SYMBOLS 11 ... Computer, 12 ... Data reading part, 13 ... Memory | storage device, 14 ... CPU, 21 ... Difference calculating part, 22 ... Area division part, 23 ... Number acquisition part, 24 ... Encoding process part, 25 ... Compression information generation part 31 ... Electronic camera, 33 ... Image sensor, 34 ... Image processing engine, 35 ... ROM, 37 ... Recording I / F, 39 ... Storage medium

Claims (9)

A difference calculation unit for obtaining a prediction difference of pixels of the processing target image;
A predetermined value is obtained based on the magnitude of the prediction difference of the pixel, a variable-length first code indicating a remainder obtained by dividing the absolute value of the prediction difference by the predetermined value, and the absolute value of the prediction difference is the predetermined value An encoding processing unit that obtains a variable-length second code indicating a quotient divided by the value and a fixed-length third code indicating the sign of the prediction difference;
A compression information generating unit that arranges the first code, the second code, and the third code in a predetermined order to generate compression information of the processing target image;
An image compression apparatus comprising: The image compression apparatus according to claim 1.
The encoding processing unit obtains an encoding number n based on the size of the prediction difference of the pixel, 2 ⁿ is set as the predetermined value,
The compression information generation unit is an image compression device that associates pixel information in which the first code, the second code, and the third code are arranged in a predetermined order with the encoding number n. The image compression apparatus according to claim 2,
An area dividing unit that divides the processing target image into a plurality of areas;
The image compression device, wherein the encoding processing unit obtains the encoding number n for each region based on an average value of absolute values of the prediction differences of the plurality of pixels in the region. The image compression apparatus according to claim 3.
When the average value of the absolute values of the prediction differences is M, the encoding processing unit,
An image compression apparatus in which the value of a variable N that is an integer of 0 or more that minimizes the value of “((M + 0.5) / 2 ^N ) + N” is the encoding number n. The image compression apparatus according to any one of claims 2 to 4,
The encoding processing unit continues one binary code up to a quotient value obtained by dividing the absolute value of the prediction difference by 2 ⁿ , and attaches the other binary code to the end of the one code. An image compression apparatus for generating the second code. An imaging unit that captures a subject and obtains a processing target image;
An image pickup apparatus comprising: the image compression apparatus according to any one of claims 1 to 5.   A program for causing a computer to operate as the image compression apparatus according to any one of claims 1 to 5.   The processing target generated by causing the computer to execute the compression information of the processing target image generated by the image compression apparatus according to any one of claims 1 to 5, or the program according to claim 7. An image expansion device that expands image compression information. A program that causes a computer to operate as the image expansion device according to claim 8.

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