JP2007060000A - Device and program for compressing data, and data transfer system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a data compressing device, a data transfer system, and a data compression program, which transfer electronic data smoothly. <P>SOLUTION: There are provided: a compression section for performing first compression processing including the quantization processing of a gradation value to electronic data; and an output section for performing second compression processing to the electronic data subjected to the first compression processing for outputting when the first compression processing achieves a prescribed compression goal, and for outputting the electronic data subjected to the first compression processing as they are, when the first compression processing fails to attain the prescribed compression goal. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a data compression apparatus that performs compression processing on electronic data, a data transfer system that performs compression processing on electronic data, transfers the decompression processing, and a data compression program that performs compression processing on electronic data.

  Along with recent advances in information and communication technology, not only text information but also image information such as photographs and pictures has been handled as electronic data, and in the industry that prints a large amount of printed matter such as printing, such electronic data An image represented by (image data) is often printed using a DFE (Digital Front End Processor) connected to the DFE and suitable for mass printing.

When performing such mass printing, it is important to smoothly transfer image data from the DFE to the printer in order to improve the efficiency of printing work. Therefore, a style is often employed in which image data is subjected to compression processing to reduce the amount of data, image data is transmitted to a printer, and image data expansion processing is performed before printing. Reference 1 and Patent Document 2). In such compression processing of image data, more redundancy is achieved based on the process of compressing by quantizing the tone value of the image represented by this image data, the characteristics of the data arrangement of the image data (eg appearance frequency), etc. In some cases, compression is performed through a two-stage compression process, that is, a process of compression by encoding (Huffman encoding) that performs code allocation with a low code allocation. The image data compressed through the two-stage compression process in this way is transmitted to the printer, and a two-stage decompression process corresponding to the two-stage compression process is performed at the time of printer output. The image is printed.
JP-A-6-113145

  Of these two stages of decompression processing, decompression processing of image data compressed by Huffman coding is complicated and time-consuming, and this decompression processing is used to transfer image data, such as the flow of image data being clogged in the middle. This may cause problems and reduce the efficiency of the printing operation.

  Such a problem is not a problem that occurs only when two-stage compression processing, that is, compression processing by quantization and compression processing by Huffman coding, but is a problem that generally occurs when multi-stage compression processing is performed.

  In view of the above circumstances, an object of the present invention is to provide a data compression apparatus, a data transfer system, and a data compression program that make electronic data transfer smooth.

In order to achieve the above object, a data compression apparatus of the present invention comprises:
A compression unit that performs a first compression process on the electronic data;
When the first compression process achieves a predetermined compression target, the electronic data subjected to the first compression process is output after being subjected to a second compression process. And an output unit that outputs the electronic data subjected to the first compression process as it is when the process does not achieve a predetermined compression target.

  If the electronic data to be decompressed is not sufficiently compressed at the stage where the decompressed electronic data is subjected to the decompression process, the amount of data when the decompression process is actually performed is the data before the compression process is performed. Since it does not change much compared to the amount, the effect of increasing the amount of data by the decompression process is small, and the data output efficiency is poor. Even when the output efficiency is poor, the processing capacity of the hardware or software that performs the decompression process is usually sufficient, so this is not a problem, but it supports multi-stage compression processing. In the case of multi-stage decompression processing, if the decompression process before the decompression process with poor output efficiency takes time, a synergistic decrease in efficiency occurs, and the output data amount becomes insufficient when viewed as a whole decompression process. This may interfere with printing.

  In the data compression apparatus of the present invention, since the compression is insufficient in the first compression process which is the preceding compression process among all the compression processes, the output efficiency of the decompression process corresponding to the first compression process is poor. In this case, since the data is output without performing the second compression process in the subsequent stage, a synergistic decrease in efficiency due to the decompression process corresponding to the second compression process is avoided, contributing to efficient electronic data transfer. Will do.

  In the data compression apparatus of the present invention, “the electronic data is page data representing a page having an image composed of a plurality of pixels each having a gradation value, and the compression unit A form in which the first compression process including the quantization process is performed and the output unit performs the second compression process including the Huffman coding is a preferable form.

In general, when compression processing by Huffman coding is performed, it is known that it takes time to decode and decompress the Huffman-coded electronic data. For this reason,
If the output efficiency of the decompression process corresponding to the first compression process is poor, if there is a Huffman decoding with a further poor output efficiency in the previous stage of the decompression process, a synergistic decrease in efficiency occurs, and the entire decompression process is performed. As a result, the amount of output data becomes insufficient, and printing may be hindered.

  According to the preferred embodiment of the data compression apparatus, the electronic data without the need for Huffman decoding is output, so that the processing efficiency is good and the processing speed of the electronic data is improved.

  In the data compression apparatus according to the present invention, “when the electronic data is page data representing a page and the first compression process achieves a predetermined compression target, For each data part representing each of the plurality of parts, the data part that has been subjected to the first compression process is further subjected to the second compression process and output, and the first compression process is performed in a predetermined manner. A form in which, when the compression target is not achieved, the data portion subjected to the first compression process is output as it is "is also a preferable form.

  Even if the data compression apparatus of such a form includes a data portion that partially reduces the degree of compression by performing compression processing for each data portion, Processing is performed without overlooking the low degree of compression of the data portion.

To achieve the above object, the data transfer system of the present invention comprises:
A compression unit that applies a first compression process to the electronic data including a quantization process of the gradation value;
When the first compression process achieves a predetermined compression target, the electronic data subjected to the first compression process is output after being subjected to a second compression process. If the process does not achieve a predetermined compression target, the data compression apparatus includes an output unit that outputs the electronic data subjected to the first compression process as it is, and the electronic data output from the data compression apparatus If the received electronic data is electronic data that has been subjected to the second compression processing, the electronic data is subjected to decompression processing corresponding to the second compression processing and output, and the received electronic data is output. When the data is electronic data that has not been subjected to the second compression process, a second data processing unit that outputs the data as it is;
And a data decompression device including a first data processing unit that performs decompression processing corresponding to the first compression processing on the electronic data output from the second data processing unit.

  The data compression apparatus according to the present invention has an output efficiency of the decompression process corresponding to the first compression process because sufficient compression is insufficient in the first compression process that is the preceding compression process among all the compression processes. However, if the second compression process is not performed, a synergistic decrease in efficiency due to the decompression process corresponding to the second compression process is avoided, and electronic data can be transferred efficiently.

In order to achieve the above object, a data compression program of the present invention comprises:
Built into a computer system,
Effective to calculate a second device value as an effective device value at the time of output with respect to a first device value that is a device value representing the amount of each of the N device colors and is a setting value for output. A value calculation program,
On that computer system,
A compression unit that applies a first compression process to the electronic data including a quantization process of the gradation value;
When the first compression process achieves a predetermined compression target, the electronic data subjected to the first compression process is output after being subjected to a second compression process. When the process does not achieve a predetermined compression target, an output unit that outputs the electronic data subjected to the first compression process as it is is constructed.

  By executing the data compression program of the present invention in a computer system, the data compression apparatus of the present invention can be easily realized.

  It should be noted that the data compression program referred to in the present invention is only shown in its basic form here, but this is only for avoiding duplication, and the data compression program referred to in the present invention is limited to the above basic form. Rather, various forms corresponding to the above-described forms of the data compression apparatus are included.

  Further, the elements such as a compression unit constructed on the computer system by the data compression program of the present invention may be one element constructed by one program part, and one element may be constituted by a plurality of program parts. It may be constructed, or a plurality of elements may be constructed by one program part. In addition, these elements may be constructed so as to execute such an action by themselves, or may be executed by giving instructions to other programs and program components incorporated in the computer system. It may be constructed.

  According to the data compression device, the data transfer system, and the data compression program of the present invention, the transfer of electronic data is smooth.

  Hereinafter, an embodiment of a data compression device of the present invention, an embodiment of a data transfer system, and an embodiment of a data compression program will be described.

  FIG. 1 is a diagram showing an embodiment of a data transfer system of the present invention to which an embodiment of a data compression apparatus of the present invention is applied.

  FIG. 1 shows a data transfer system 10 including a DFE (Digital Front End Processor) 100 and a BEP (Back End Processor) 200, and is a transfer destination of image data in the data transfer system 10. A printer 20 is also shown. The DFE 100 and the BEP 200 are connected by a general-purpose interface cable 150 for SCSI, and the BEP 200 and the printer 20 are connected by a dedicated interface cable 260. This data transfer system 10 corresponds to an example of the data transfer system of the present invention.

  In the DFE 100, bitmap data is generated by performing RIP (Raster Image Processing) processing on image data described in a page description language. Further, in the DFE 100, this bitmap data is subjected to compression processing to generate compressed data. This compressed data is transferred from the DFE 100 to the BEP 200 via the general-purpose interface cable 150. The operation performed by the DFE 100 to compress the bitmap data and transfer the compressed data to the BEP 200 is an operation as an embodiment of the data compression apparatus of the present invention.

  In BEP200, this compressed data is decompressed, and bitmap data that is substantially equivalent to uncompressed bitmap data is generated. Then, the generated bitmap data is delivered to the printer 20, and the printer 20 outputs an image based on the bitmap data. The operation performed by the BEP 200 to deliver the bitmap data generated by decompressing the compressed data to the printer 20 is the operation as the data decompression device in one embodiment of the data transfer system of the present invention.

  Hereinafter, the DFE 100 and the BEP 200 will be described. First, the DFE 100 will be described.

  FIG. 2 is a hardware configuration diagram of the DFE shown in FIG.

  The DFE 100 includes a CPU 211 that executes various programs, a main memory 212 that is read out and stored for execution by the CPU 211, and a hard disk device 213 that stores various programs and data. Is provided. The DFE 100 has a FD loading port 111 shown in FIG. 1 and a CD-ROM loading port 112 shown in FIG. 1 into which a CD-ROM 2150 is loaded. In each loading slot, an FD drive and a CD-ROM drive shown in FIG. 2 for driving the loaded FD and CD-ROM are provided.

  The DFE 100 further includes an image display device 120 for displaying a screen, a keyboard 130 for inputting user instructions and character information in the DFE 100, and an arbitrary position on the display screen when the screen is displayed. Thus, a mouse 140 for inputting an instruction corresponding to the position is provided. Various elements described above are connected to each other via a bus 1200.

  Further, a BEP 200 and a printer 20 connected to the BEP 200 shown in FIG. 1 are provided outside the DFE 100, and an output interface 217 is sent to the DFE 100 in order to send compressed image data to the BEP 200. Is built-in. The DFE 100 is provided with an input interface 216 to which an external device such as a scanner is connected. Image data can also be input to the DFE 100 through the input interface 216. The output interface 217 and the input interface 216 are also connected to the above-described various elements constituting the hardware of the DFE 100 via the bus 1200.

  Next, an embodiment of the data compression program of the present invention will be described.

  When one embodiment of the data compression program of the present invention is stored in the CD-ROM 2150, for example, when the CD-ROM 2150 is loaded into the main body 110 from the CD-ROM loading slot 112, the CD-ROM 2150 is loaded. A data compression program stored in the hard disk drive 213 of the DFE 100 is installed by the CD-ROM drive 215. When the data compression program installed in the hard disk device 213 is activated, the DFE 100 operates as an embodiment of the data compression device of the present invention.

  FIG. 3 is a diagram showing an embodiment of the data compression program of the present invention.

  Here, the data compression program 900 is stored in the CD-ROM 2150. The storage medium for storing the data compression program 900 according to the present invention includes not only the CD-ROM 2150 and the hard disk device 213 but also various storage media such as the FD 2150 and a DVD or MO (not shown in FIG. 2). It can be adopted.

  The data compression program 900 is executed in the DFE 100 shown in FIGS. 2 and 3, and operates the DFE 100 as an embodiment of the data compression apparatus of the present invention as described above. The image data generation unit 511 , A first compression unit 512, a compression rate determination unit 513, a compression processing branching unit 514, and a second compression unit 515. Detailed contents of each element of the data compression program 900 will be described later.

  FIG. 4 is a diagram showing elements constructed on the DFE and the components of the BEP shown in FIG. 1 in order to operate the DFE shown in FIG. 1 as an embodiment of the data compression apparatus of the present invention.

  When the data compression program 900 shown in FIG. 3 is installed in the DFE 100 shown in FIG. 1, the image data generation unit 311, the first compression unit 312, the compression rate determination unit 313, and the compression processing branch in the DFE 100 shown in FIG. Each element of the unit 314 and the second compression unit 315 is constructed on the DFE 100, and operates the DFE 100 as an embodiment of the data compression apparatus of the present invention. These image data generation unit 311, first compression unit 312, compression rate determination unit 313, compression processing branch unit 314, and second compression unit 315 are the first compression unit 512 in the data compression program 900 shown in FIG. The compression rate determination unit 513, the compression processing branching unit 514, and the second compression unit 515 are each constructed on the DFE 100. Accordingly, each element in FIG. 3 corresponds to each element in FIG. 4, and each element in FIG. 4 is a combination of the hardware of the DFE 100 shown in FIGS. 1 and 2 and the OS and application program executed by the DFE 100. 3 is different in that each element of the data compression program 900 shown in FIG. 3 is composed only of application programs.

  Here, in order to clarify the difference between the present embodiment and the prior art, configurations of the conventional DFE and BEP will be described.

  FIG. 5 is a diagram showing components in the conventional DFE and BEP.

  In FIG. 5, the same components as those in the DFE 100 and the BEP 200 shown in FIG. 4 are denoted by the same reference numerals. As is apparent from this figure, conventionally, after the image data is compressed by the first compression unit 312 and the second compression unit 315 in the conventional DFE 100 ′, the second decompression in the conventional BEP 200 ′ is performed. Unlike the configuration shown in FIG. 5, the compression process and the expansion process are not branched in the middle.

  Based on the above facts, each component shown in FIG. 4 and its operation will be described below.

  First, the elements of the DFE 100 will be described.

  As shown in FIG. 4, the DFE 100 includes a CPU 211 and an image data transmission unit 330. In this figure, an image data generation unit 311, a first compression unit 312, a compression rate determination unit 313, a compression processing branching unit 314, and a second compression unit 315 are shown in the CPU 211. It represents operating as a generation unit 311, a first compression unit 312, a compression rate determination unit 313, a compression processing branching unit 314, and a second compression unit 315. The CPU 211 controls the operation of the entire DFE 100. Here, the operation of the CPU 211 will be described by focusing on the portion directly related to the present invention.

  First, the CPU 211 operating as the image data generation unit 311 generates bitmap data by performing RIP processing on image data representing a two-dimensional array of a plurality of pixels for one page or a plurality of pages. Is done.

  In addition, the CPU 211 operating as the first compression unit 312 performs compression processing by dividing the generated bitmap data for one page into block units called an array of pixels for eight rows in the page. In this compression processing, the amount of information about gradation is reduced by quantizing the Fourier coefficient when the gradation value in the block is Fourier-series-expanded with a spatial frequency using a predetermined quantization table. Thus, the amount of bitmap data is compressed.

Specifically, this quantization is performed by dividing the Fourier coefficient by the numerical value on the quantization table corresponding to the spatial frequency of the Fourier coefficient, rounding down the decimal part of the quotient, and then again calculating the numerical value of the quantization table. Done by multiplying.

  In this quantization process, many of the high-frequency Fourier coefficients are quantized to the value “0”. As a result, in the image represented by the bitmap data, a fine level that is difficult to be recognized by human vision. Tone changes are cut off, and conversely large gradation changes that are easily recognized by human vision remain. After such quantization, the value “0” is further encoded by encoding information (so-called run length) indicating how many Fourier coefficients having the value “0” are continuously arranged. The information about the Fourier coefficient is reduced, and the amount of bitmap data is further compressed. Hereinafter, the compressed data at this stage is referred to as first compressed data.

  Further, in the CPU 211 operating as the compression rate determination unit 313, the first compression unit 312 has not yet processed the first compressed data generated by sequentially compressing each block unit of an array of 8 rows of pixels. A compression rate for compression bitmap data is sequentially obtained, and it is determined whether or not the compression rate has reached a predetermined target compression rate. In accordance with this determination result, the CPU 211 operating as the compression processing branching unit 314 branches subsequent processing of the first compressed data.

  In this embodiment, it is determined whether or not the compression rate has reached a predetermined target compression rate for each block unit, that is, an array of pixels for eight rows in this way. However, the present invention determines the compression rate. It may be performed in units of pages, or may be performed every N blocks (N is an integer of 2 or more).

  In this determination, when the compression rate has reached the target compression rate, the generated first compressed data in block units is compared with the Huffman by the CPU 211 operating as the second compression unit 315. Encoding is performed to further compress the amount of data. Hereinafter, the compressed data at this stage is referred to as second compressed data. The second compressed data compressed with the Huffman coding is transferred to the image data transmitting unit 330, and the CPU 211 outputs the compressed data to the BEP 200 to the image data transmitting unit 330. To instruct.

  On the other hand, if the compression rate does not reach the target compression rate in this determination, the generated first compressed data in block units is directly passed to the image data transmission unit 330 without being subjected to Huffman coding. The CPU 211 instructs the image data transmission unit 330 to output the first compressed data to the BEP 200.

  In the image data transmission unit 330, when the CPU 211 instructs the output of the first and second compressed data, the output of the compressed data in accordance with the SCSI is started toward the BEP 200.

  In the above description, the CPU 211 corresponds to an example of a compression unit according to the present invention, and the combination of the CPU 211 and the output unit 330 corresponds to an example of an output unit according to the present invention.

  Next, the BEP 200 will be described.

  As shown in FIG. 4, the BEP 200 includes an image data receiving unit 410, an expansion processing branching unit 431, a first expansion unit 433, a second expansion unit 432, and an image data output unit 450.

  The image data receiving unit 410 of the BEP 200 receives the first and second compressed data transmitted from the output unit 330 of the DFE 100 according to the SCSI. Then, these first and second compressed data are transferred to the decompression processing branching unit 431. In the decompression processing branching unit 431, the compressed data is the first compressed data or the second compressed data. In response to this, branching of the subsequent expansion processing is performed.

  When the compressed data is the second compressed data, the second compressed data is transferred from the decompression processing branching unit 431 to the second decompressing unit 423, and is encoded by the Huffman in the second decompressing unit 423. The data is decrypted into the original data and the data is decompressed. Therefore, at this stage, the second compressed data returns to the first compressed data. Subsequently, the first compressed data is sent to the first decompression unit 433, and the run length decoding of “0” that has been encoded is performed in the first decompression unit 433. Inverse Fourier series expansion is performed, and bitmap data representing the gradation value of each pixel is reproduced. The bitmap data is sent by the image data output unit 450 to the printer 20 provided outside the BEP 200 and output from the printer 20.

  When the compressed data is the first compressed data, the first compressed data is sent from the expansion processing branching unit 431 to the first expansion unit 433 as it is, and is encoded by the first expansion unit 433. The run-length decoding for “0” that has been performed is performed, and further, inverse Fourier series expansion is performed, so that bitmap data representing the gradation value of each pixel is reproduced. The bitmap data is sent by the image data output unit 450 to the printer 20 provided outside the BEP 200 and output from the printer 20.

  Regardless of whether the compressed data of the BEP 200 is the first compressed data or the second compressed data, the decompressed bitmap data representing the image output from the printer 20 is processed by the first compressing unit 312. Because of this quantization, the data amount is reduced compared to the original image data generated by the image data generation unit 311 in the DFE. However, since most of the reduced data amount is a high frequency component of the spatial frequency, the reduction in image quality due to the reduction in the data amount is hardly felt by human vision.

  In the above description, the combination of the image data receiving unit 410, the expansion processing unit branching unit 431, and the second expansion unit 432 corresponds to an example of the second data processing unit according to the present invention, and the first expansion unit. 433 corresponds to an example of the first data processing unit referred to in the present invention.

  The above is the description of the embodiment of the present invention.

  As described above, in the present embodiment, since the process of whether to perform Huffman coding is branched according to the compression rate of the first compressed data, the expansion capability of the second expansion unit 432 in the BEP 200 is Even in the case of low, the efficiency reduction due to the low decompression capability and the reduction in efficiency of the decompression process in the first decompression unit 433, which occurs because the compression ratio of the first compressed data is not sufficient, are combined. Can be avoided.

  Further, in the data transfer system 10 and the data transfer system 10 of the present embodiment, the compression rate is determined for each block unit, so that the degree of compression is partially reduced in the bitmap data to be compressed. Even when the image data portion is included, the low degree of compression of the image data portion is confirmed without being overlooked, and is appropriately processed for each image data portion.

  Furthermore, the data transfer system 10 according to the present embodiment does not require expensive parts such as a high-performance decompressor that can execute a high-speed decompression process, which causes an increase in manufacturing cost. Is suppressed.

  In the above description, as an example of the data compression apparatus according to the present invention, the compression process is executed in units of blocks called an array of pixels for 8 rows. However, the data compression apparatus of the present invention is, for example, the above compression process Alternatively, the compression processing may be executed in units other than the block units described above.

  In the above description, the CPU 211 is described as an example of the compression unit according to the present invention. However, the data compression unit of the present invention may be, for example, a dedicated circuit that performs such compression processing.

  Further, in the above description, the image data transmission unit 330 that once plays the role of the output unit according to the present invention performs output in accordance with SCSI, but the output unit of the present invention is not limited to this. A device that outputs in accordance with a communication standard other than SCSI may be used. In this case, the receiving unit referred to in the present invention receives the compressed data in accordance with the same communication standard other than SCSI as the transmitting side.

It is a figure showing one Embodiment of the data transfer system of this invention with which one Embodiment of the data compression apparatus of this invention was applied. It is a hardware block diagram of DFE shown in FIG. It is a figure which shows one Embodiment of the data compression program of this invention. FIG. 2 is a diagram showing elements constructed on the DFE and components of the BEP shown in FIG. 1 in order to operate the DFE shown in FIG. 1 as an embodiment of the data compression apparatus of the present invention. It is the figure showing the component in the conventional DFE and BEP.

Explanation of symbols

10, 10 'data transfer system 20 printer 100, 100' DFE
150 General-purpose interface cable 200, 200 'BEP
260 Dedicated interface cable 111 FD loading port 112 CD-ROM loading port 120 Image display device 130 Keyboard 140 Mouse 1200 Bus 211, 211 ′ CPU
212 Main memory 213 Hard disk device 214 FD drive 2140 FD
215 CD-ROM drive 2150 CD-ROM
216 Input interface 217 Output interface 900 Data compression program 511 Image data generation unit 512 First compression unit 513 Compression rate determination unit 514 Compression processing branch unit 515 Second compression unit 311 Image data generation unit 312 First compression unit 313 Compression Rate determination unit 314 Compression processing branch unit 315 Second compression unit 330 Image data transmission unit 410 Image data reception unit 431 Expansion processing branch unit 432 Second decompression unit 433 First decompression unit 450 Image data output unit

Claims (5)

A compression unit that performs a first compression process on the electronic data;
When the first compression process achieves a predetermined compression target, the electronic data subjected to the first compression process is output after being subjected to a second compression process. A data compression apparatus comprising: an output unit that outputs the electronic data subjected to the first compression process as it is when the process does not achieve a predetermined compression target. The electronic data is page data representing a page having an image composed of a plurality of pixels each having a gradation value,
The compression unit performs a first compression process including a quantization process of the gradation value,
2. The data compression apparatus according to claim 1, wherein the output unit performs a second compression process including Huffman coding. The electronic data is page data representing a page,
The output unit, when the first compression process achieves a predetermined compression target, for each data part representing each of the plurality of parts of the page, to the data part subjected to the first compression process On the other hand, after the second compression process is performed, the data is output. When the first compression process does not achieve a predetermined compression target, the data portion subjected to the first compression process is output as it is. The data compression apparatus according to claim 1, wherein the data compression apparatus is a device. A compression unit that performs a first compression process including quantization of the gradation value on electronic data;
When the first compression process achieves a predetermined compression target, the electronic data subjected to the first compression process is output after being subjected to a second compression process. If the process does not achieve a predetermined compression target, the data compression apparatus includes an output unit that outputs the electronic data subjected to the first compression process as it is, and the electronic data output from the data compression apparatus If the received electronic data is electronic data that has been subjected to the second compression processing, the electronic data is subjected to decompression processing corresponding to the second compression processing and output, and the received electronic data is output. When the data is electronic data that has not been subjected to the second compression process, a second data processing unit that outputs the data as it is;
A data transfer comprising: a data decompression device comprising: a first data processing unit that performs decompression processing corresponding to the first compression processing on the electronic data output from the second data processing unit system. Embedded in a computer system,
A compression unit that performs a first compression process including quantization of the gradation value on electronic data;
When the first compression process achieves a predetermined compression target, the electronic data subjected to the first compression process is output after being subjected to a second compression process. A data compression program that constructs an output unit that outputs the electronic data subjected to the first compression process as it is when the process does not achieve a predetermined compression target.

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