JPH07170410A - Color image data compression method - Google Patents

Abstract

PURPOSE:To attain efficient compression of color image data whose notation scale exceeds binary with the simple method employing the run length coding compression technology aiming at a conventional binary image. CONSTITUTION:Color information is read in the unit of horizontal lines, and a comparator means 32 compares the read color information with that of a preceding line as to whether or not they are identical to each other. Then a same color discrimination means 33 discriminates whether or not all pixels have the same color, a compression arithmetic means 34 counts number of pixels in the compression unit being consecutive pixels having same color information, replaces the count into a numeral or bits having specific values whose number is equal to the pixel number. Then the processing is sequentially repeated as to all compression units in the horizontal lines to generate compression data, and finally a data length comparison means 35 compares a compressed data quantity with a data quantity before compression and when the compression data quantity is not less than the data quantity before compression, the data before compression are adopted for compressed data in this color image data compression method.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for compressing color image data such as color graphic display data used in personal computers and the like, and more particularly to a method for compressing color image data capable of compressing color image data by a simple method. Regarding

[0002]

2. Description of the Related Art Conventionally, an image data compression method for binary image data such as FAX is digitized (sampling / quantized) in the process of scanning and photoelectric conversion, and 1 (black), 0.
A typical run length encoding / compression technique is to replace a continuous length (run length) of black or white pixels in a picture signal converted into a (white) pulse with a code (Ohm Co., Ltd., "Image information compression" Supervised by Hiroshi Harashima, p150
Issued August 25, 1991, see).

[0003]

However, although the above-mentioned conventional image data compression method can be applied to the compression technique of monochrome image data for only two colors (binary) of black and white, the compression of color image data is performed. As for the technology, since compression including color information is not considered,
There is a problem in that color image data cannot be compressed by the conventional run-length coding compression technique.

Various color compression techniques are also applied to color image data (Nikkei Electronics 1993, 5-
10 no. 580 "Data compression technology" p93, see)
However, all of the compression techniques are complicated and there is a problem in that color image data cannot be easily compressed.

The present invention has been made in view of the above situation, and color image data having more than two values can be easily processed by a simple method to which a conventional run-length coding / compression technique for binary images is applied. It is an object of the present invention to provide a color image data compression method capable of efficient compression.

[0006]

According to a first aspect of the present invention for solving the above-mentioned problems of the prior art, color information is read in horizontal line units from image data of one screen, and the color information of the previous line and processing are performed. The line data comparison processing step of comparing the color information of the target line with the color information of the target line, and if the color information of the target line is the same, the command indicating that the color information is the same as the color information of the previous line is used as the compressed line data. When the color information and the color information of the processing target line are not the same, it is determined whether all the pixels in the processing target line have the same color information. If the same color information, all the pixels have the same color information. The same color determination processing step in which the command indicating that there is and the color information are compressed line data and all pixels in the processing target line are the same. If the color information is not the color information, the compression operation is performed using consecutive pixels having the same color information as the compression unit, and the result of repeatedly performing the compression operation on all the compression units in the processing target line is sequentially added and compressed. A value of the data length of the compressed data is compared by comparing the value of the data length of the compressed data with the value of the data length before the compression operation after the compression operation processing step of creating data and the execution of the compression operation processing step. Is smaller, the command meaning the data subjected to the compression calculation process, the value of the data length of the compressed data, and the compressed data are the compressed line data, and when the value of the data length of the compressed data is not smaller, A data length comparison processing step in which the command meaning the data before the compression operation and the data before the compression operation are compressed line data It is characterized by a door.

According to a second aspect of the present invention for solving the above-mentioned problems of the conventional example, the compression operation processing step according to the first aspect uses the compression unit as compression unit data obtained by performing compression operation processing on the compression unit. A color change bit indicating the beginning of a block, color information in the compression unit, a block / non-block information bit indicating the type of the following pixel continuity information, and pixel continuity information indicating the number of pixels in the compression unit. Within the compression unit, the color change bit is set, the color information of the compression unit is set, and the boundary of the compression unit is detected by the change of the color information of the pixel to create the compression unit data to be constructed. If the number of pixels in the counted compression unit is larger than the number of bits of the pixel continuous information,
The block / non-block information bit is set as block information, and the number of pixels is set as a numerical value as the subsequent pixel continuity information to create compression unit data, and the number of pixels is larger than the number of bits of the continuous pixel information. If not, the block / non-block information bit is set as non-block information, and the subsequent bits of the pixel continuity information are set with bits having a specific value equal to the number of pixels to create compression unit data. It is characterized in that the compression unit data is added by repeatedly performing the compression calculation for all the compression units in the processing target line to create the compressed data for one line.

[0008]

According to the present invention, the color information is read from the image data of one screen in units of horizontal lines, the color information of the previous line and the color information of the line to be processed are compared, and if they are the same, the previous A command and color information that means that all pixels have the same color information if all the pixels in the line to be processed have the same color information Are used as compressed line data, and in other cases, consecutive pixels having the same color information are used as compression units, and repeated compression operations are performed for all compression units in the line to be processed, and the results are sequentially added to obtain compressed data. Is created and the data length of the compressed data is compared with the data length before the compression operation, and if the data length of the compressed data is smaller, the compression operation is performed. The command meaning the processed data, the data length of the compressed data and the compressed data are the compressed line data, and if the data length of the compressed data is not smaller, the command meaning the data before the compression operation and the compressed operation. Since the color image data compression method uses the previous data as the compressed line data, the compressed data is created without performing a complicated compression operation on the line of the same color information as the previous line and the line of the same color for all pixels. It is possible,
Also, after the compression operation, the data length before and after compression is compared, and the data with the smaller data length value is adopted as the compressed data, so the conventional run-length encoding compression technology for binary images is applied. The color image data can be easily and efficiently compressed by the simple method described above, and the compression efficiency can be improved especially for images with little color change, and the line of the pattern that does not improve the compression effect by the compression operation is included. However, the compression can be performed without degrading the compression efficiency.

According to a second aspect of the present invention, the compression calculation processing step according to the first aspect divides the color information in units of horizontal lines into compression units made up of consecutive same color pixels, and performs the compression calculation. The number of pixels in the compression unit is counted until the boundary of is detected by the change of the color information of the pixel, and the number of pixels is set numerically or has a specific value equal to the number of pixels depending on the size of the number of pixels. As a color image data compression method in which compressed line data is created by substituting bits, and compressed line data is added by repeatedly performing compression operation for all compression units in the processing target line to create compressed line data for one line. Therefore, compressed line data can be created with simple logic that replaces the number of consecutive pixels of the same color with numerical values. Can be, it can be easily compressed color image data exceeding the binary in a simple manner of applying run-length encoding compression techniques a conventional binary image to the subject.

[0010]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described with reference to the drawings. FIG. 1 is a conceptual configuration block diagram for realizing a color image data compression method according to an embodiment of the present invention.

In the image data compression method of this embodiment, as shown in FIG. 1, an image data area 10 for storing color image data for one screen and an image to be subjected to compression processing on the color image data in the image data area 10. Data compression means 30
And a compressed image data area 60 for storing the compressed image data, and a line data area for taking in image data in horizontal line units from the image data area 10 and performing compression processing in the image data compression means 30. 21, a line data save area 22, a line data number area 23, and a compressed line data area 50 are provided, and the same color for detecting the compression unit and performing compression calculation in the image data compression processing 30. A counter 40, a compressed data length counter 41, a pixel pointer 45, a color information save area 46, and a compressed data work area 47 are provided.

On the other hand, inside the image data compression means 30 for performing the compression processing in units of horizontal lines, a header creation means 31 is provided.
, Line data comparison means 32, and same color determination means 33
A compression calculation means 34, a data length comparison means 35, and a line data output means 36 are provided.

Further, the configuration of each part in FIG. 1 will be specifically described. The image data area 10 is an area for storing image data for one screen. The image data in the image data area 10 is made up of a plurality of pixels (pixels), and the size of the color information indicating the display color of each pixel varies depending on the system to which the pixel is applied, and therefore the description will be made here with N bits. Normally, the data in the image data area 10 is read from a storage medium by a personal computer or the like, or image data transmitted from the outside through a communication line or the like is stored for each screen.

Next, the line data area 21 is an area in which the image data for one screen stored in the image data area 10 is read and stored in horizontal line units under the control of the image data compression means 30. The line data save area 22 saves the data in the line data area 21 after the compression processing is completed, and the line data comparing means 32 compares the line data to be processed with the previous line. It is used for the purpose.

In the line data number area 23, the number of pixels of the horizontal line of the image data stored in the image data area 10 is set in advance, which is used when detecting the end of the processing for each line, or It is used when comparing the data length before compression and the data length after compression after the completion of the compression operation.

Next, the compressed line data area 50 is an area for storing the compressed data for one line which has been subjected to the compression processing, and the inside is composed of a command area 51 and a data area 52. However, if the compressed data length is larger than the pre-compression data length when the compression calculation process is completed for one line, the pre-compression data is used as it is, and the compressed data with the command added is stored. It has become so.

The compressed image data area 60 is an area for storing the compressed image data for one screen which has been subjected to the compression processing. At the end of the compression processing for each line, the compressed line is output by the operation of the line data output means 36. Data area 5
The compressed data is written line by line from 0, and when the compression processing for one screen is completed, the compressed data is recorded from the area to a storage medium or transmitted through a communication line or the like.

The format of the compressed image data stored in the compressed image data area 60 will be described with reference to FIG. FIG. 2 is a format diagram showing the format of compressed image data in the image data compression method of this embodiment. As shown in FIG. 2, the compressed image data in the image compression method of this embodiment is composed of a header section 61 and a line data section 62. The header section 61 relates to the entire data such as a file name and a checksum. Information is recorded, and compressed data for each horizontal line is recorded in the line data portion 62 for the horizontal line.

The compressed line data for each horizontal line of the line data section 62 is further composed of a command section 63 and a data section 64, and the command section 63 indicates the compression type of the data of the subsequent data section 64. Command (CM
D) is set. Specific commands (CMD) and formats of the line data section 62 corresponding to the commands include the following. 1) Command "LINE REPEAT" --- When the data is exactly the same as the previous line Format CMD (LINE REPEAT) only 2) Command "LINE FILL" --- When all lines have the same color Format CMD (LINE FILL) + Color information 3) Command "CMP" --- When compressed calculation processing is applied Format CMD (CMP) + Compressed data length + Compressed data 4) Command "ORG" --- Format as it is CMD (ORG) + color information (original data remains)

Next, the format of the compressed data when the compression calculation processing is performed will be described in detail with reference to FIG. FIG. 3 is a format diagram showing the format of the compressed data when the compression calculation processing in the image data compression method of this embodiment is performed. In the compression operation processing in the image data compression method of the present embodiment, compression operation is performed by performing compression operation using up to 16 consecutive pixels having the same color information as a compression unit to generate compression unit data, and The compressed data in which the compression unit data are arranged in order for all the compression units is created. The maximum value of the number of pixels of the same color forming the compression unit is 16 because the pixel continuity information is represented by 4 bits or less.

Therefore, the format of the compressed data when the compression operation is performed in the image data compression method of the present embodiment is, as shown in FIG. 3, a color change bit indicating the start of the compression unit data, color information, and The block / non-block information bit and the pixel continuity information are used as one set of compression unit data, and the compression unit data is repeated by the number of compression units in one line.

If the number of consecutive pixels having the same color information exceeds 16, compression unit data is created by dividing the compression unit by the 16th pixel, and subsequent pixels are compressed to the next compression unit. It is supposed to be processed as.

Next, each component in the compression unit data will be described. First, the color change bit is located at the head of each compression unit data and indicates that the color information has changed and the compression unit has changed, and its value is fixed to "1".

The color information is the information indicating the color of the compression unit, and the color information indicating the color of the pixel of the image data before compression is adopted as it is. Since the number of constituent bits changes according to the system to which it is adapted. , Here, it is explained as N bits.

The block / non-block information bit is an information bit indicating whether the succeeding pixel continuity information is a block or a non-block. In the case of a block, "1" is set to set the non-block information. In the case, "0" is set.

The pixel continuity information represents the number of pixels in the compression unit by a numerical value or a sequence of values "0" of the same number of bits as the number of pixels, and the bit length is 1 to 4 bits. That is, in the case of a block, the pixel continuity information is treated as 4-bit numerical data, and the number of pixels included in the compression unit is set by a 4-bit numerical value. In the case of a non-block,
The value "0" of the same number of bits as the number of pixels included in the compression unit is continuously set in the pixel continuity information.

Next, the same color counter 40 is a counter for counting the number of consecutive pixels of the same color forming the compression unit in the image data compression means 30, and the compressed data length counter 41 is for one line. Is a counter that counts the length of compressed data (compressed data length) in bit units.

The pixel pointer 45 is a pointer indicating the position of the pixel of the color information to be read from the line data area 21 in the compression calculation means 34, and the color information save area 46 is the change position of the color information. This is an area for temporarily saving the information set in the color information in the compression unit data in order to detect the.

The compressed data work area 47 is a work area in which the compressed data is sequentially set in the process of the compression calculation process, and the compression calculation process for one line is completed, and the value of the compressed data length is before the compression. If it is smaller than the value of the data length of, the compressed line data area 50 is set in the data area 52.

Next, each means in the image data compression means 30 will be described. The header creating means 31 is a means for creating the header portion 61 of the head portion of the compressed image data,
Information about the entire data such as the file name and checksum of the compressed image data is created, and the compressed image data area 60 is created.
It is designed to output to.

Next, the line data comparing means 32 is means for judging whether the line data to be processed is exactly the same as the immediately preceding line data, and specifically, it is read into the line data area 21. The line data to be processed is sequentially compared with the immediately preceding line data saved in the line data save area 22, and if they are exactly the same, the command "LI" meaning the same data as the previous line
NE REPEAT "is set in the command area 51 of the compressed line data area 50.

Next, the same color judging means 33 is a means for judging whether or not all the line data to be processed have the same color. Specifically, the same color judging means 33 The color information of the line data is sequentially checked, and if all pixels have the same color information, the command "LINEF" which means the same color
ILL "is set in the command area 51 of the compressed line data area 50, and the color information is set in the data area 52.

Next, the compression calculation means 34 is means for performing compression calculation processing when the line data to be processed is neither the same as the previous line nor has the same color, and the same color information is obtained. Consecutive pixels are used as a compression unit, compression unit data to be created for each compression unit is sequentially added to the compression data work area 47, compression processing is repeated for all compression units in the line data, and compression data at the end The compressed data of the line to be processed is set in the work area 47.

Here, the compression calculation processing for each compression unit is, specifically, the number of pixels included in the target compression unit is counted using the same color counter 40, and the block / non-block is determined according to the value of the number of pixels. Is determined and the pixel continuity information is set.

When the number of consecutive pixels having the same color information exceeds 16, the compression unit is once divided into 16th pixels to create compression unit data.

Then, in the course of the compression process, the compressed data length counter 41 is used to accumulate the compressed data length, and when the compression calculation is completed for all the compression units of the line to be processed, the value of the compressed data counter 41 is compressed. It indicates the data length.

Next, the data length comparison means 35 is means for comparing the length of the compressed data created by the compression calculation means 34 with the length of the data before compression, and more specifically, the value of the compressed data length counter 41. And the data length before compression (the number of line data x color information length N bits) are compared, and if the value of the compressed data length is smaller, the command means the data that has been subjected to the compression calculation processing. CMP "is set in the command area 51 of the compressed line data area 50, and the value of the compressed data length counter 41 and the data of the compressed data work area 47 are set in the data area 52.

On the contrary, when the value of the data length before compression is the same as or smaller than the value of the compressed data length, the data before compression having a small amount of data is adopted and the command "ORG" meaning the original data is compressed. The line data area 50 is set in the command area 51, and the line data area 21 is set in the data area 52.

The line data output means 36 converts the data in the compressed line data area 50 into the compressed image data area 60.
Then, the data in the post-output line data area 21 is copied to the line data save area 22 to prepare for the next process.

Next, the flow of processing in the image data compression method of this embodiment will be specifically described with reference to FIGS. FIG. 4 is a flow chart showing the flow of processing of the image data compression method of this embodiment. In FIG. 4, the image data for one screen is already stored in the image data area 10, and the process until the compressed image data is stored in the compressed image data area 60 is shown. N bits.

As shown in FIG. 4, the process flow of the image data compression method of the present embodiment is as follows. First, as the initial process, the file header creating means 31 creates a file header and writes it in the compressed image data area 60 ( 100), the line data save area 22 is cleared (102), then image data for one line is read from the image data area 10 into the line data area 21 (110), and the compressed line data area 50 is cleared (112). ), The line data comparing means 32 compares the line data in the line data area 21 with the line data in the line data saving area 22 (120). It is determined whether all pixels have the same color (130), and if they are not the same color, compression calculation means. 4 performs compression processing (14
0), the data length comparison means 35 performs data length comparison processing (150).

Next, the compressed line data area 50 is written to the compressed image data area 60 (160), and the data in the line data area 21 is saved in the line data save area 22.
(162), it is judged whether the compression processing has been completed for all the lines of the image data area 10 (170), and if the compression processing has not been completed for all the lines, the processing 110
Return to, if the compression process is completed for all lines, 1
The image compression process for the screen ends.

In the process 120, the line data in the line data area 21 and the line data save area 22 are stored.
If the line data of the same line is exactly the same, the command area 51 of the compressed line data area 50 indicates the same data as the previous line, "LINE REPEA".
T "is set (122), and the process moves to 160.

When all the pixels in the line data area 21 have the same color in the process 130, the command "LINE FILL" meaning the same color is set in the command area 51 of the compressed line data area 50 (132). , The color information having the same color is set in the data area 52 (134), and the process 160 is performed.

Next, the flow of the compression calculation process (process 140 of FIG. 4) of the image data compression method of this embodiment will be described with reference to FIGS. 1 and 5 to 9. FIG. 5 is a flow chart showing an outline of the flow of compression calculation processing of the image data compression method of the present embodiment, FIG. 6 is a flow chart showing the flow of line unit initial processing, and FIG. 7 is a compression unit. 9 is a flowchart showing a flow of initial processing, and FIG.
[Fig. 9] is a flowchart showing a flow of a count process of the same color pixel number, and Fig. 9 is a flowchart showing a flow of a compression information creating process.

The outline of the flow of the compression calculation process (process 140 of FIG. 4) of the image data compression method of this embodiment is as shown in FIG.
Next, the compression unit is initialized (210), the same color pixel number is counted (220), the compression information is created (230), and finally the pixel pointer 4
It is judged whether the value of 5 is larger than the line data number area 23 (240).
Since all the data of 1 has been subjected to the compression processing, the processing is terminated, and when the data is not large, the processing returns to the processing 210 which is the initial processing of the compression unit to perform the processing of the next compression unit.

Next, in the line-by-line initial processing (processing 200 in FIG. 5) of this embodiment, as shown in FIG. 6, the compressed data length counter 41 is cleared (320) and 1 is set in the pixel pointer 45. Then, the color information for one pixel is read from the line data area 21 (330) (3
40), the initial processing for each line is completed.

Next, in the initial process of the compression unit (process 210 in FIG. 5) of this embodiment, as shown in FIG. 7, the color change bit "1" is first set in the compressed data work area 47 (400). Then, the read color information is set (410), the same color counter 40 is set to 1 (420), the read color information is saved in the color information save area 46 (430), and the compressed data length counter is set. (1 + N) bits (the number of color change bits + the number of color information bits) are added to 41 (440), and the initial process of the compression unit is completed.

Next, in the counting process of the same color pixel number (process 220 of FIG. 5) of this embodiment, as shown in FIG. 8, 1 is added to the pixel pointer 45 (500) and the value of the pixel pointer 45 is added. Is larger than the value in the line data number area 23 (510), and if not larger, one pixel of color information is read from the line data area 21 (520), and then the end of the compression unit is detected by color change. It is determined whether the color information read for that purpose is the same as the color information save area 46 (530). If the color information is the same, the same compression unit is added, so 1 is added to the same color counter 40 (540), and the next compression is performed. In order to check whether the maximum number of pixels of the unit is exceeded, it is judged whether the value of the same color counter 40 is larger than 16 (550), 1
When it is not larger than 6, the process returns to the process 500, and when it is larger than 16, the compression unit is switched, so that the count process of the same color pixel number is ended.

In the process 510, if the value of the pixel pointer 45 is larger than the value of the line data number area 23, it means that all the data in the line data area 21 has been read. When the read color information is not the same as the color information save area 46 in the processing 530, the color information of the pixel is changed and the compression unit is switched, so that the counting processing of the same color pixel number is ended.

Next, the compressed information creation processing of this embodiment (see FIG.
In processing 230), it is determined whether the value of the same color counter 40 is larger than “4” as shown in FIG. 9 (6
00), if it is larger, as a process of treating pixel continuous information as a block, "1" is set as a block / non-block information bit in the compressed data work area 47 (610), and the value of the same color counter 40 is set to a 4-bit numerical value. To the compressed data work area 47 (62
0), "5" (block /
The number of bits of non-block information + the number of bits of continuous pixel information) are added (630), and the compression information creation process is terminated.

On the other hand, in the process 600, when the value of the same color counter 40 is "4" or less, the block / non-block information bit "0" is stored in the compressed data work area 47 as the process of treating the pixel continuous information as a non-block. "(660), and the same color counter 4
The value "0" is stored in the compressed data work area 47 by the number of 0s.
Is set (670), and the compressed data length counter 41 is set to "
1 ″ (the number of bits of block / non-block information) + the value of the same color counter 40 is added (680), and the compression information creating process is ended.

Next, regarding the flow of the data length comparison processing (processing 150 in FIG. 4) of the image data compression method of this embodiment,
This will be described with reference to FIGS. FIG. 10 is a flow chart showing the flow of data length comparison processing of the image data compression method of this embodiment. In FIG. 10, the color information length of one pixel is described as N bits. The flow of the data length comparison processing of the image data compression method of this embodiment is shown in FIG.
As shown in, the data length before compression (the value of the line data number area 23 × N bits) is compared with the value of the compressed data length counter 41 (700), and the value of the compressed data length counter 41 is If it is smaller, the command "CMP" which means the data subjected to the compression calculation processing is set in the command area 51 of the compression line data area 50 (71
0), the value of the compressed data length counter 41 is set in the data area 52 of the compressed line data area 50 (72
0), the data in the compressed data work area 47 is set following the data area 52 (730), and the data length comparison process is ended.

On the other hand, in the process 700, when the value of the compressed data length is the same as the value of the data length before compression or the value of the compressed data length is larger, the command "ORG" meaning the original data is set to the compressed line data. The command area 51 of the area 50 is set (740), and the data of the line data area 21 is set in the data area 52 (75).
0), the data length comparison process ends.

According to the image data compression method of this embodiment,
Image data of one screen composed of color information exceeding two values is edited in units of horizontal lines, and consecutive pixels having the same color information are used as a compression unit, or the number of pixels in the compression unit is replaced with a numerical value or pixels. Since it is designed to replace with bits having the same number as the specific value, it is possible to easily compress color image data by a simple method that applies the conventional run-length coding compression technology for binary images. In particular, there is an effect that the compression efficiency can be improved particularly for an image with little color change.

Further, according to the image data compression method of the present embodiment, after the compression operation is performed for each horizontal line of the image data, the data length after compression and the data length before compression are compared to determine the data length. Since the one with the smaller value is adopted, even if the image data contains a line of a pattern that does not improve the compression effect due to the compression operation, the compression efficiency is not deteriorated by that, and the effect that the data can be compressed efficiently There is.

Further, according to the image data compression method of the present embodiment, before performing a complicated compression operation, a command indicating that the line constituted by the same color information as the previous line is the same is used. Only compressed data, 1
If all the lines have the same color, the command indicating that they are the same color and the compressed data of only that color information are used. Therefore, in the case of image data with few color changes, the compression efficiency is improved and the compression processing efficiency is also improved. There is an effect that can be improved.

[0058]

According to the first aspect of the present invention, color information is read from the image data of one screen in horizontal line units, and the color information of the preceding line and the color information of the line to be processed are compared and found to be the same. For example, a command that means that the same color information as the previous line is used as compressed line data, and if all the pixels in the line to be processed have the same color information, a command that means that all the pixels have the same color information. Color information and compressed line data,
In other cases, using consecutive pixels with the same color information as the compression unit, the compression operation is repeated for all the compression units in the line to be processed, and the results are sequentially added to create compressed data. The data length is compared with the data length before the compression operation, and if the data length of the compressed data is smaller, the command meaning the data after the compression operation and the data length of the compressed data and the compression data are compressed line. If the data length of the compressed data is not smaller than the data of the previous line, since the compressed image data is the command that indicates the data before the compression operation and the data before the compression operation is the compressed line data. Compressed data can be created without applying complicated compression calculation to lines of the same color information and lines of the same color for all pixels. After the calculation, the data length before and after compression is compared, and the data with the smaller data length value is used as the compressed data, so it is easy to apply the run-length coding compression technology for conventional binary images. It is possible to easily and efficiently compress color image data with various methods, and especially to improve the compression efficiency for images with little color change,
Further, even if a line of a pattern that does not improve the compression effect is included by the compression calculation, the compression can be performed without degrading the compression efficiency.

According to the second aspect of the present invention, the compression calculation processing step according to the first aspect divides the color information in units of horizontal lines into compression units made up of consecutive same color pixels, and performs compression calculation. The number of pixels in the compression unit is counted until the boundary of is detected by the change of the color information of the pixel, and the number of pixels is set numerically or has a specific value equal to the number of pixels depending on the size of the number of pixels. As a color image data compression method in which compressed line data is created by substituting bits, and compressed line data is added by repeatedly performing compression operation for all compression units in the processing target line to create compressed line data for one line. Therefore, compressed line data can be created with simple logic that replaces the number of consecutive pixels of the same color with numerical values. It can be readily embodiment offers the advantage of being able to compress the color image data exceeding the binary simple method applying the run-length encoding compression techniques a conventional binary image to the subject.

[Brief description of drawings]

FIG. 1 is a conceptual configuration block diagram for realizing a color image data compression method according to an embodiment of the present invention.

FIG. 2 is a format diagram showing a format of compressed image data in the image data compression method of the present embodiment.

FIG. 3 is a format diagram showing a format of compressed data when a compression calculation process is performed in the image data compression method of the present embodiment.

FIG. 4 is a flowchart showing a processing flow of an image data compression method of this embodiment.

FIG. 5 is a flowchart showing an outline of the flow of compression calculation processing of the image data compression method of this embodiment.

FIG. 6 is a flowchart showing a flow of a line unit initial process in the compression calculation process of the image data compression method of the present embodiment.

FIG. 7 is a flowchart showing a flow of a compression unit initial process in the compression calculation process of the image data compression method of the present embodiment.

FIG. 8 is a flowchart showing a flow of counting processing of the same color pixel number in the compression calculation processing of the image data compression method of the present embodiment.

FIG. 9 is a flowchart showing a flow of compression information creation processing in the compression calculation processing of the image data compression method of this embodiment.

FIG. 10 is a flowchart showing the flow of data length comparison processing of the image data compression method of this embodiment.

[Explanation of symbols]

10 ... Image data area, 21 ... Line data area, 22 ... Line data save area, 23 ... Line data number area, 30 ... Image data compression means, 31 ...
Header creating means, 32 ... Line data comparing means, 3
3 ... Same color determination means, 34 ... Compression calculation means, 35 ...
Data length comparison means, 36 ... line data output means,
40 ... Same color counter, 41 ... Compressed data length counter, 45 ... Pixel pointer, 46 ... Color information save area, 47 ... Compressed data work area, 50 ...
Compressed line data area, 51 ... Command area, 5
2 ... data area, 60 ... compressed image data area,
61 ... Header part, 62 ... Line data part, 63 ... Command part, 64 ... Data part

Claims (2)

[Claims] 1. Color information is read in units of horizontal lines from image data of one screen, and it is compared whether the color information of the previous line and the color information of the processing target line are the same. If they are the same, it is the same as the previous line. When the line data comparison processing step in which the command meaning that the color information is the compressed line data is the color information of the preceding line and the color information of the processing target line are not the same,
It is determined whether all the pixels in the line to be processed have the same color information, and if they are the same color information, the command which means that all the pixels have the same color information and the color information are the same as the compressed line data. If all pixels in the color determination processing step and the processing target line do not have the same color information, a compression operation is performed using consecutive pixels having the same color information as a compression unit, and all the pixels in the processing target line are processed. A compression operation processing step of sequentially adding results of repeated compression operations for compression units to create compressed data, and a value of the data length of the compressed data and a data length before the compression operation after the compression operation processing step is executed. Of the compressed data, and if the value of the data length of the compressed data is smaller, it means that the compressed data has been processed. And the data length value of the compressed data and the compressed data are compressed line data, and when the data length value of the compressed data is not smaller, the command meaning the data before the compression operation and the command before the compression operation And a data length comparison processing step of using the above data as compressed line data. 2. The compression operation processing step according to claim 1, wherein, as compression unit data obtained by performing compression operation processing on a compression unit, a color change bit indicating the beginning of the compression unit, and color information on the compression unit. , A color change bit is set to create compression unit data composed of block / non-block information bits indicating the type of the following pixel continuity information and pixel continuity information indicating the number of pixels in the compression unit. Then, the color information of the compression unit is set, the number of pixels in the compression unit is counted until the boundary of the compression unit is detected by the change of the color information of the pixel, and the number of pixels in the counted compression unit is If the number of bits of the pixel continuity information is greater than,
The block / non-block information bit is set as block information, and the number of pixels is set as a numerical value as the subsequent pixel continuity information to create compression unit data, and the number of pixels is larger than the number of bits of the continuous pixel information. If not, the block / non-block information bit is set as non-block information, and the subsequent bits of the pixel continuity information are set with bits having a specific value equal to the number of pixels to create compression unit data. A color image data compression method, characterized in that compression data is added repeatedly by repeatedly performing compression operation for all compression units in a line to be processed to create compressed data for one line.