JPH08186503A - System and device for compressing/extending data - Google Patents

Abstract

PURPOSE: To provide satisfactory data compressibility for the image data of gradation expressions and to make time for extension in the case of providing restored data correspondent to output speed requested by external equipment. CONSTITUTION: A compressing part 4 starts compression from the head of image data equivalent to one line for each compression format while preparing plural kinds of compression formats composed of data compression formats by utilizing the continuity of bit values in data concerning the image data equivalent to one line from an image memory 21, selects the compression format storing the maximum number of data as compressed data and performs the compression of data equivalent to one line by repeating the same operation concerning the next compression starting position data as well. An extending part 5 discriminates whether compressed records equivalent to each line are compressed data or source data and restores the data later by using a restoring method decided by the compression format but outputs the source data as they are.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a data compression / expansion system and a data compression / expansion processing device.

[0002]

2. Description of the Related Art Conventionally, in a print output device such as a printer or a plotter, generally, when outputting, all image data is expanded in an image memory before printing. However,
Such a method has a problem that an enormous size of image memory is required as the size of a printout device and the resolution thereof are increased.

For example, about 36 MB (megabytes) of memory is required to output an image of one A0 size image having a resolution of 400 DPI, and long printing of about 15 to 20 feet is realized. About 135 to
Since a memory of 180 MB must be mounted, there is a problem that the cost burden increases.

In order to solve such a problem, that is, in order to output long data such as long printing without increasing the amount of image memory, the image data is compressed and temporarily stored and expanded while printing. It can be realized. Here, as one of conventional image data compression methods, there is a run-length encoding method. Run length coding method is "0" or "1"
Is a data compression method in which image data is compressed by non-fixed length coding by counting the number of consecutive binary data and assigning a code corresponding to the number of consecutives from a predefined code table. In a device that uses coded data compressed by the run length coding method, the compressed coded data is stored in a storage device, and the coded data stored at the time of output is read out and output as restored data by decoding. In this case, the speed of the composite processing depends on the code length of each encoded data read from the storage device. Therefore, since the coding rate is high in the high compression rate portion and low in the low compression rate portion, inconvenience may occur depending on the device that processes the restored data. Specifically, an output device that needs to keep the speed of the restored data constant, for example,
In printers, plotters, CRTs, etc., there is a problem that the output speed must be suppressed during the decoding time of the coded data that is the slowest to decode.

On the other hand, the "data compression / expansion method" described in Japanese Patent Laid-Open No. 1-273429 discloses a unit (for example, one block) in which data before compression (hereinafter referred to as original data) is designated at the data compression stage. ) For each non-fixed length, calculate the data compression rate of the encoded data for each unit, and compare it with the given standard compression rate. If the calculated data compression rate is higher than the standard compression rate, "encode" The encoded data is stored in the storage device together with the identification data meaning "", and if it is low, the original data is stored together with the identification data meaning "non-coded", and at the decoding (that is, decompression of compressed data) stage. The encoded data is decoded and output, and the uncoded data (that is, the stored original data) is output as it is, so that the restoration speed of the non-fixed length code in the specified unit is kept above a certain value. Get too It is set to.

[0006]

Here, as a problem of the prior art, in the method of requiring a memory as large as the size to be output as described above, the length of a print output device for a long image is long. In the shaku data output device, the output memory (image memory) becomes enormous and the cost burden becomes large. In the data compression method by the run length coding method as described above, continuity is provided in binary data of "0" or "1". There is a drawback that the compression effect cannot be expected for image data that has no gradation and that the compressed data amount becomes extremely larger than the original data amount in some cases. If a phenomenon that becomes more extremely large occurs, it becomes difficult to keep the expansion time for a predetermined unit length L within the scanning time of an output device such as a laser printer. JP-A-1-273429 "Data compression and according to
In the "expansion method", the condition for maintaining the decompression speed of the non-fixed length code in the specified unit at a certain value or higher is the above-mentioned "reference compression ratio" with respect to the data compression ratio of the encoded data in the compression stage. Since the lowest compression rate that can achieve the decompressed data output speed required by the output device using the "data compression / decompression method" is registered, the data compression / decompression method based on the above "data compression / decompression method" is temporarily registered. When connecting an output device such as a printer as an external device to the decompression processing device, in order to correspond to the type and output speed of the output device, the decompression data output speed is set for each specified speed of the connectable external device. There is an inconvenience that it is necessary to obtain and register the lowest feasible compression rate or to calculate it in the device, and to calculate the compression rate of encoded data (when calculating the compression reference value above). Since requires the calculation including) such complicated arithmetic operations that the hardware of the device based on the "Data compression and decompression method" is difficult, there is.

The present invention was devised to solve the above problems, and a first object is to provide binary data of "0" or "1" which is a characteristic of the conventional run length coding system. Good data compression performance for continuous image data and realization of data compression performance for gradation-represented image data that is difficult to compress with the run length method, and when decompressing data It is to provide a data compression / decompression method capable of making the decompression time when decoding the restored data correspond to the output speed required by an external device,
A second object is to provide a data compression / decompression processing device capable of outputting long data by a long printing device such as a printer or a plotter and other output devices without increasing the output memory.

[0008]

In order to achieve the above object, the data compression method of the first invention uses a plurality of types of fixed-length compression formats in which encoding formats are defined in advance.
After the original data is encoded in each compression format from the first compression start position for each predetermined unit L, the compression format with the maximum number of encoded original data is selected from each compression format as compressed data. , A new compression start position is obtained by adding the number of the above-mentioned encoded original data to the previous compression start position, and the encoding for each compression format from the compression start position and the selection of the compression format are repeated to obtain an element for each predetermined unit L. It is characterized in that a compressed data string of data is generated.

In a second aspect of the present invention, in the data compression method of the first aspect, when the number of original data encoded by the selected compression format is smaller than a predetermined value, a length corresponding to a predetermined unit value from the compression start position. Is provided with a compression format for storing the original data.

A third aspect of the present invention is the data compression method according to the second aspect, wherein after generating a compressed data string from the original data of a predetermined unit L, the length of the compressed data string and the length of the original data of the predetermined unit L are set. In comparison, when the length of the compressed data string is shorter than the length of the original data of the predetermined unit L, the identification data is added to the head of the compressed data string and output together with the compressed data string, and the length of the compressed data string is the predetermined unit. When it is not shorter than the length of the original data of L, the identification data is added to the head of the original data string of the predetermined unit L and output.

According to a fourth aspect of the present invention, it is determined whether the next succeeding data is a compressed data sequence or original data based on the identification data output by the data compression method of the third aspect of the invention. The original data is restored for each type and output in synchronism with the output synchronization signal, and in the case of the original data string, it is output in synchronism with the output synchronization signal.

According to a fifth aspect of the present invention, in a data compression / expansion processing device, at least a control unit for controlling transfer of data and original data for each predetermined unit L that is sequentially received are provided for each predetermined unit L by the data compression method of claim 3. Of the original data and a compressed data string having the identification data as the head or an original data string of a predetermined unit L having the identification data as the head, and the identification data generated by the compression unit as the head. The storage unit that sequentially stores the compressed data sequence or the original data sequence, and the compressed data sequence starting with the identification data stored in the storage unit or the original data sequence starting with the identification data are sequentially received and the identification is performed. Determines whether the following data is a compressed data string or an original data string. If the data is a compressed data string, restores the original data according to the type of compressed data and outputs from the external device. Output in synchronization with the period signal, and having a, a decompression unit for outputting in synchronization directly with the output sync signal from the external device when the original data string.

[0013]

With the above structure, in the data compression methods of the first and second inventions, the original data for each predetermined unit L is compressed to the first compression start position by a plurality of types of fixed-length compression formats in which the encoding format is defined in advance. After each is encoded in each compression format, the compression format with the maximum number of encoded original data is selected from each compression format to be the compressed data, so the conventional run-length encoding method does not compress. A good compression result can be obtained even for image data that is difficult to express in gradation.

In the data compression method of the third invention, since the original data string is output as an exceptional process when the capacity of the compressed data exceeds the amount of the original data, the upper limit is set in the compressed data capacity and the predetermined unit is set. The processing time when decompressing the decompressed data for L can be kept constant.

In the data decompression method of the fourth invention, since the compressed data string generated by the data compression method of the third invention corresponds to each predetermined unit length of the original data, the synchronization signal from the external output device is used. It becomes possible to repeat stable decompression processing within a fixed time based on the above, and the interface with an external output device becomes easy. Further, the decompressed data can be output without re-expanding to the image memory.

In the data compression / expansion processing device of the fifth invention, since the compressed data string generated by the data compression method of claim 3 corresponds to each predetermined unit length of the original data, the expanded data is stored in the image memory. It is possible to output without re-expansion, it is possible to repeatedly perform stable expansion processing within a fixed time with reference to the synchronization signal from the external output device, and it is easy to interface with the external output device.

[0017]

1 is a block diagram showing the configuration of an embodiment of a data compression / expansion processing apparatus using the data compression / expansion method of the present invention. , Transfer control unit 3, compression unit 4, and decompression unit 5
And a storage unit for storing data. The storage unit may be an auxiliary storage device (external storage device) connected via a bus when the data compression / expansion processing device 19 is one component of the computer device as shown in FIG.

FIG. 2 shows the data compression / expansion processing apparatus 1 of FIG.
1 is a block diagram showing a configuration example of a long-size printing apparatus as an example of a computer system having a configuration of 0. FIG.
2, the system bus interface (I / F) unit 1 of FIG.
Further, the output interface (I / F) unit 6 may be provided on either the data compression / expansion processing device 19 side or the print output device 23 side. FIG. 3 is a development view of the image data (raster data) of M bits × N lines on the image memory 21.

In FIG. 1 and FIG. 2, the control instruction analysis unit 2 analyzes the control instruction from the CPU 20 fetched through the system bus interface unit 1 and gives a necessary instruction to the transfer control unit 3. For example, at the time of compression processing, the image data expanded in the image memory 21 is captured and the compression unit 4
The compressed data and the identification data output from the compression unit 4 are stored in the storage unit such as the auxiliary storage device 22. Further, at the time of decompression processing, identification data and compressed data are taken from the auxiliary storage device 22 and passed to the decompression unit 5, and the image data decompressed by the decompression unit 5 is output to the print output device 23 such as a printer or a plotter via the output interface 6. To do. In the present embodiment, when the CPU is used in the control command analysis unit 2, the CPU and the CPU 20 of FIG. 2 are configured separately, but it is also possible to use the same CPU. The control command analysis unit 2 and the transfer control unit 3 may be configured as one control unit.

The transfer control unit 3 receives an image from the image memory 21 for the compression unit 4 at the time of compression according to an instruction from the control instruction analysis unit 2.
Of the image data from the compression unit 4 and the transfer of the compressed record for one line from the compression unit 4 (referred to as the compressed data string starting with the identification data or the original data) to the auxiliary storage device 22 and decompressed when decompressing the data. External device via the transfer control of the compressed record for one line from the auxiliary storage device 22 to the unit 5 and the output interface unit 6 of the image data restored by the decompression unit 5 (for example, the print output device 23 in FIG. 2). Output control to.

The compression unit 4 compresses one line of image data (raster data) transferred from the image memory 21 under the control of the transfer control unit 3. As will be described later (see FIG. 7), the compression process is composed of a plurality of formats such as a format for performing data compression using the continuity of the bit values of image data and a compression format for performing data compression using the repetition of bit patterns. 4 types of compression formats (see FIGS. 4 (a) to 4 (c)) are prepared, and the number of the same type of data or the repetition of the pattern formed by the continuous data from the compression start position (described later) of the image data for one line , And stores the number and the type or pattern of data in each (type-specific) compressed format (see FIG. 5),
The compression format that stores the maximum number of data is selected as compressed data, the same operation is repeated for the next consecutive data to form a compressed data string for one line, and then the compressed data string is stored in the auxiliary storage device 22. Output (see FIG. 8) after determining whether to store the original data string for one line in the auxiliary storage device 22.

Under the control of the transfer control unit 3, the decompression unit 5 determines whether the compressed record string for each line received from the auxiliary storage device 22 is the compressed data or the original data string, based on the identification data. Data is decompressed by a decompression method determined by the compression format, and the original data string is kept as it is, in synchronization with the synchronization signal from the external device received by the transfer control unit 3 via the output interface unit 6, and via the output interface unit 6. It is output to an external device (for example, the print output device 23).

FIG. 4 is a diagram showing an example of a compression format used in the compression unit 4. Each compression format is composed of 32 bits, and each compression format has 2 to 4 bits for identifying each format in the compressed data at the time of decompression. It comprises a control bit section 41 and a data description section (compressed format length-control bit length). The data description section has a different structure depending on the type of compression format as described below. The compression format size is 32 bits long in this embodiment, but is not limited to this, and may be 16 bits or a multiple of 8, for example. Also, the control bit length is not limited to 2 to 4 bits, and can be adjusted according to the number of types of compression formats.

In FIG. 4A, since the data compression is performed by utilizing the continuity of bit values like the image data of FIG. 5A, the continuous data type of the image data and the count value for each data type Is one example of a compression format that is capable of storing data. In this example, four data bits (in this example, each data bit is 0 for discriminating continuous continuous data of one line of image data of the same type) are used. ”
4-1 to 42-4, which is composed of 1 bit taking a value of "1", and a portion (hereinafter, counter value storage portion) 43-1 to store the number of data corresponding to each data bit.
It is a compression format having 43-4 (hereinafter referred to as a type 1 compression format).

In the example of FIG. 4A, the compression format is 6
Although there are four bit (maximum count value = 63) counter value storage units, the compression format size of Type 1 is 32 bits, and when the size of each counter value storage unit is the same. Can prepare compressed format data having a counter value storage section of 3 to 9 bits (maximum count value = 7 to 511) and 7 to 3 control bits. Further, the count value storage unit may be configured to store the number counted by another counter, or the count value storage unit itself may be used as each counter.

In the present embodiment, in addition to the compression format having four 6-bit counter value storage units, the type 1 has seven 3-bit counter value storage units, and the four 4-bit counter value storage units. Prepared, and one having three 9-bit counter value storage units, the size of each counter value storage unit in the compressed format is taken into consideration in consideration of the variety of change points of image data for one line. Compressed format data configured differently (for example, a compressed format having a 4-bit, 9-bit, 9-bit, and 4-bit counter value storage unit) may be prepared, depending on the compressed format size and the purpose of use. Therefore, various types of compression formats of type 1 may be prepared.

FIG. 5 shows an example of compression of image data according to the type 1 compression format. When the bit string of FIG. 5A is compressed using the compression format of FIG.
As shown in (b), the first bit after the control bit 41
"0" corresponding to white is entered as a data bit, the number of white bits 50 is stored in the count value storage unit 43-1, and the bit values corresponding to consecutive bits are similarly stored in the third to fourth data bits. Is entered, and the count value storage unit 43-2
The number of consecutive bits is stored in 43 to 43-3 to form compressed data based on the 32-bit type 1 compression format.

The compression format of FIG. 4B is shown in FIG.
This is a compression format effective for image data in which a bit string having a certain pattern is repeated continuously like the image data in (a). The compression format in this case is the control bit 42 and the number of times the pattern is repeated. The data description section has a section 52 and a reference pattern storage section 53 (hereinafter referred to as a type 2 compression format).

Further, in the compression format of FIG. 4C, the total Ti of the values (numbers) stored in each count value storage of each compression format of type 1 is used.
Is a compression format selected when Ti <compressed data size-control bit = R, and stores R-bit original data (raster data string) (hereinafter, referred to as type 3 compression format).

In this embodiment, the compressed data size is 32 bits, the number of control bits is 2 bits, and the original data of 30 bits is stored in the compression format of type 3 as shown in FIG. 6 (that is, this embodiment). Then, in principle, when the number of data for one format compressed by each type 1 compression format and type 2 compression format is less than 30 in any compression format (see FIG.
Type 3 compression format is used). The type 3 compression format is provided to improve the compression efficiency when the number of compressed data in type 1 and type 2 is equal to or smaller than the compression format size.

FIG. 7 is a flow chart showing an embodiment of the compression processing in the compression unit 4. First, as described above, the image data for one line transferred from the image memory 21 under the control of the transfer control unit 3 is processed. Upon reception, the data number counter C is set to 0 and the compression start position counter D is set to 1 (step S0). Since the number of data for one line is known, it is not necessary to provide the data number counter D, but in the present embodiment, the data number counter D for processing the final data for one line is provided.

In step S1, the data description part of all compression formats (all of the type 1 compression formats that have been set (prepared) and the compression formats of type 2 and type 3) are initialized, and each compression format is initialized. The total compression number counter FCi (i is 1 to the number of compression formats) is initialized for each and the process proceeds to step S2.
As will be described later, the total compression counter FCi calculates a compression start position counter D value for selecting a compression format in which data is most compressed into one format and for knowing the data position at which the next compression is started. However, since it is possible to know the number of compressed data in each format without providing the total compression counter FCi (for example, in the case of type 1, it is sufficient to add up the respective counter values of the compression formats). Alternatively, regardless of the total compression number counter FCi, the most compressed compression format may be selected and the data position for starting the next compression may be calculated.

In step S2, the total compression counter F
Using the value of Ci as the compression start position of the data for one line,
The compression is executed for each compression format, the data number counter C counts, and the total compression number counter FCi counts the compression number for each compression format. Then, the process proceeds to step S3. For example, the type 1 compression format is a type 1-1 having seven 3-bit counter value storage units, and a type 1-2 having six 4-bit counter value storage units and a 6-bit counter value storage unit 4 Assuming that the type 1-3 has three and the type 1-4 has three 9-bit counter value storage units, the types 1-1 to 1-1
For the compression formats 1-4, the continuity of the data bit values from the compression start position is used to count the continuous data of the same type up to the maximum number of stored values in the counter value storage unit, and the count value and the data bit are counted. To store. This operation is repeated up to the number of repeatable numbers (counter value storage units) of each compression format,
Data is compressed by storing the continuous data count value in the counter value storage unit for the repeatable number of each compression format and setting the corresponding data bit.

With regard to the type 2 compression format, the data is compressed by extracting a repeating pattern of data from the compression start position and storing the number of patterns and the pattern. In the case of the type 3 compression format, when the number of pieces of compressed data (value of the total compression counter FCi) by other compression formats is less than the fixed number R (30 in this embodiment), the fixed number of data is from the compression start position. Store the data as is in the storage location of the format. However, the continuous number of continuous data for one line may be less than R, and in this case, if the format 3 is used, the decompression unit 5 is inconvenient to process, so the type 1 or type 2 compression format is used. Use as is. Also, in the image data for one line,
If the image data of one line is completed before a certain compression format is fixed, 0 (zero) is temporarily added,
Complete the compressed data. For this compressed data, 0 data of M bits or more is processed as invalid data at the time of decompression processing.

In step S3, the total compression counter F
The counter FCj having the largest value is selected from the values of Ci and the content of the compression format j corresponding to the counter FCj is stored as compressed data in the auxiliary storage device (or stored in the compressed data area). Further, the value of the counter FCj is added to the compression start position counter D, the next compression start position is calculated, and the process proceeds to step S4.

In step S4, it is checked whether or not the compression for one line is completed. If the compression for one line is completed, the process proceeds to step S5. If not completed, the process returns to step S1 to proceed to the next step. The data compression operation is repeated from the compression start position based on the value of the compression start position counter D.

In step S5, the number of digits of compressed data (=
By comparing the compressed format size × the number of compressed data in the compressed data) with the number of data for one line (= the value of the counter C), it is determined whether or not the data is actually compressed in the above steps S1 to S4. If the data is actually compressed, the process proceeds to step S6, and if it is not compressed (the number of digits of the compressed data ≧ the value of the counter C), the process proceeds to step S7.

In step S6, a code indicating that the compressed data string stored in the auxiliary storage device 22 (or the storage area) is composed of the compressed data string, and the identification data storing the number of the compressed data and the like that follow. The compressed record added with is stored in the auxiliary storage device 22, and the process proceeds to step S9.

In step S7, the compressed data string stored in the auxiliary storage device 22 (or storage area) is rewritten with the original data string for one line, and in step S8 the original data for one line is formed at the beginning. The original data string added with the identification code that stores the code and the size of the original data string is stored in the auxiliary storage device 22, and the process proceeds to step S9. The compressed record and the original data string formed in steps S6 and S8 are written in a logically (or physically) continuous area of the auxiliary storage device 22, as shown in FIG. 8 is an explanatory diagram of a compressed record string or an original data string stored in the auxiliary storage device 22 by the above compression processing. In FIG. 8, the records for line 1 and line N consist of identification data and compressed data. It is shown that the records corresponding to line 2 are compressed records and are identification data and original data strings.

In step S9, it is checked whether or not the above processing has been completed for all lines of the image data, and the above processing is repeated until it is completed.

FIG. 9 is a flow chart showing an embodiment of the expansion processing in the expansion unit 5. First, step S11
At the step S12, the identification data is taken out from the auxiliary storage device 22 under the control of the transfer controller 3, and in step S12, it is determined whether the subsequent data is the compressed data or the original data string. Decompression processing is performed, and in the case of the original data string, the process proceeds to step S15 and output processing of the original data string is performed.

In step S13, the compressed data of the number indicated by the identification data is sequentially fetched from the auxiliary storage device 22, the type of the compressed format is discriminated by the control bit at the head of the compressed data, and is determined for each type of the compressed format. The data is restored by the restoration method, and the transfer control unit 3 synchronizes with the synchronization signal from the external device received via the output interface unit 6 serially (one bit at a time) through the output interface unit 6 to the external device ( For example, output to the print output machine 23), and step S1
In 4, it is checked whether the number of bits M for one line is exceeded, 1
When the number of bits for the line is output, step S17
Move to

In step S15, the original data of the number shown in the identification data is taken out from the auxiliary storage device 22, and the original data is directly synchronized with the synchronization signal from the external device which the transfer control unit 3 receives via the output interface unit 6. The output interface unit 6 is serially output bit by bit.
Is output to an external device via step S1, and it is checked in step S16 whether the number of bits M for one line has been exceeded. If the number of bits for one line has been output, the process proceeds to step S17.

In step S17, it is checked whether or not the expansion processing for all lines is completed, and the above processing is repeated until the expansion processing for all lines is completed.

FIG. 10 is an explanatory view of an embodiment of the long printing device shown in FIG. In the long printing device, the image memory 2 is used for each of the image data 101, 102, 103 in the drawing.
The image data 10 that has been expanded by 1 and then compressed by the data compression / expansion processing device 10.
The compressed data 111 of No. 1, the compressed data 112 of the image data 102, and the compressed data 113 of the image data 103 are respectively stored in the auxiliary storage device 22, and these compressed data are read from the auxiliary storage device 22 to obtain the image data 101.
Then, the expanded data is output to the print output device 23 from the first line portion of the data. As a result, image data larger than the installed image memory 21 can be output at a time (in FIG. 10, the image data 101, 102, and 103 cannot exceed the maximum image memory size, but data compression is performed). The continuous images 111 to 11 are displayed on the print output machine 23 by the compression / expansion processing by the expansion processing device 10.
3 can be printed), and an image exceeding the capacity of the image memory 21 can be printed (that is, long-length printing) without increasing the capacity of the image memory 21. In this way, since the decompressed data can be output without re-expanding it in the image memory, it can be applied not only to printers, plotters, and other printing output machines, but also to large-screen CRTs and FAX outputs.

As described above, according to the data compression / decompression method of the present invention, image data to be compressed is prepared by preparing a plurality of types of compression formats in data compression utilizing the continuity of binary data. (Raster data)
It is possible to obtain a stable compression rate regardless of the frequency of appearance of the change points of (the compression format with a large number of digits in the counter value storage section is effective for image data with few change points, and the counter for the large number of image data. A compression format with a small number of digits in the value storage is effective). Further, by outputting the original data as an exceptional process when the capacity of the compressed data exceeds the original data amount, the worst value of the compressed data per line becomes N + 1 longword, and it cannot be more than this. Number of long words for one line of image data). Further, it is possible to obtain a good compression result even for image data represented by gradation that is difficult to compress by the conventional run-length encoding method.

Further, in the present embodiment, the image data and gradation data represented by the bits "0" and "1" can be compressed as described above, but the invention is not limited to this, and a color image can also be supported. That is, in the case of color, one hue is composed of a combination of a red signal (R), a blue signal (B), and a green signal (G), so that one data bit of type 1 compressed data is one bit. It should show the color,
In addition, it is possible to express colors by using a combination of R, B, and G (six patterns) as a repeating pattern in the compression format of type 2, and the compression data of type 3 can also be applied to color data. Therefore, the data compression / expansion method of the present invention can also be applied to color images.

[0048]

As described above, the present invention has the following effects. It is possible to obtain a good compression result even for image data represented by gradation that is difficult to compress by the conventional run-length encoding method, and the data compression / expansion method of the present invention can also be applied to color images. Since the data compression / expansion processing device using the compression / expansion method does not perform complicated arithmetic operations in the compression processing or the expansion processing, hardware implementation is easy. By outputting the original data as an exceptional process when the amount of compressed data exceeds the amount of original data, an upper limit is set for the amount of compressed data and the processing time for decompressing decompressed data for one line is kept constant. be able to. Since the compressed data string corresponds to each line of the original image data, it is possible to repeat stable decompression processing within a fixed time based on the synchronization signal from the external output device, and Easy interface. Since the decompressed data can be output without re-expanding to the image memory, it is possible to suppress an increase in the cost of the image memory due to an increase in the size of a printout device such as a printer or plotter or a CRT screen. Since the decompressed data can be output without re-expanding to the image memory, not only long printing by a printing output machine such as a printer or plotter but also a large screen CRT or FA
It can also be applied to X output and the like.

[Brief description of drawings]

FIG. 1 is a block diagram showing the configuration of an embodiment of a data compression / expansion processing apparatus using a data compression / expansion system of the present invention.

FIG. 2 is a block diagram showing a configuration example of a long printing device as one embodiment of a computer system having the data compression / decompression processing device of FIG. 1 as a component.

FIG. 3 is a development view of image data of M bits × N lines on an image memory.

FIG. 4 is a diagram showing an example of a compression format used in a compression unit.

FIG. 5 is an example of compression of image data in a compression format of type 1.

FIG. 6 is an example of compression of image data according to a type 2 compression format.

FIG. 7 is a flowchart illustrating an example of compression processing in a compression unit.

FIG. 8 is an explanatory diagram of a compressed record string or an original data string record stored in an auxiliary storage device by a compression process.

FIG. 9 is a flowchart showing an example of decompression processing in a decompression unit.

10 is an explanatory diagram of an embodiment of the long-size printing apparatus of FIG.

[Explanation of symbols]

 2 control command analysis unit (control unit) 3 transfer control unit (control unit) 4 compression unit 5 decompression unit 19 data compression / decompression processing device 21 image memory 22 auxiliary storage device (storage unit) 23 print output machine

 ─────────────────────────────────────────────────── ─── Continuation of front page (72) Kenichi Sonoda 10-1 Minamikurokawa, Aso-ku, Kawasaki-shi, Kanagawa Japan Digital Research Institute Kawasaki R & D Center (72) Inventor Ryoichi Onoue Kawasaki-shi, Kanagawa 10-1 Minamikurokawa, Aso-ku Japan Digital Research Institute, Ltd. Kawasaki R & D Center

Claims (5)

[Claims] 1. A plurality of types of fixed-length compression formats in which encoding formats are defined in advance, the original data is encoded for each predetermined unit L in each compression format from the first compression start position, and then each compression format. The compression format with the maximum number of encoded original data is selected as compressed data, and the number of encoded original data is added to the previous compression start position to make a new compression start position. The data compression method is characterized in that the compression data string of the original data for each predetermined unit L is generated by repeating the encoding in each compression format and the selection of the compression format. 2. The data compression method according to claim 1, wherein when the number of original data encoded by the selected compression format is smaller than a predetermined value, the original data having a length of a predetermined unit from the compression start position is generated. A data compression method characterized in that a compression format for storing is provided. 3. The data compression method according to claim 2, wherein after generating a compressed data string from the original data of a predetermined unit L, the length of the compressed data string and the length of the original data of the predetermined unit L are compared, When the length of the compressed data string is shorter than the length of the original data of the predetermined unit L, the identification data is added to the head of the compressed data string and output together with the compressed data string. A data compression method characterized in that when the length is not shorter than the length of the data, the identification data is added to the beginning of the original data string of a predetermined unit L and output. 4. The identification data output by the data compression method according to claim 3 is used to determine whether the following data is a compressed data string or original data. A compressed data decompression method characterized in that original data is restored and output in synchronization with an output synchronization signal, and in the case of an original data string, it is output in synchronization with the output synchronization signal. 5. A control unit for controlling at least data transfer, and with respect to the original data for each predetermined unit L received sequentially, the compression and identification data of the original data for each predetermined unit L by the data compression method of claim 3 The compressed data string or the original data string for the predetermined unit L having the identification data as the head, and the compressed data string having the identification data as the head or the original data string generated by the compression unit A storage unit that sequentially stores and a compressed data string that starts with the identification data stored in the storage unit or an original data string that starts with the identification data is sequentially received, and whether the data that follows from the identification data is a compressed data string. It is judged whether it is the original data string, and if it is the compressed data string, the original data is restored according to the type of compressed data and output in synchronization with the output synchronization signal from the external device. In the case of, the data compression / decompression processing device is characterized by having a decompression unit that outputs the data in synchronization with the output synchronization signal from the external device.