JPH05304613A - Image data compression / decompression method and image data compression / decompression device - Google Patents

Abstract

(57) [Summary] [Object] To provide an image data compression / decompression method and an image data compression / decompression device that perform efficient and efficient compression / decompression. [Structure] Image data is divided into a plurality of pixel groups for each horizontal line, a plurality of predetermined compression processes are performed for each pixel group, and a VDP 14 and CPU 11 that select a compression pattern that is the minimum compressed data, control ROM 12 for storing programs, RAM 13 for storing various compression / expansion pattern data and corresponding number data, VDP 1
4 and a VRAM 15 for storing related information of the compression pattern selected by the CPU 11. As a result, the image data is compressed so that the compressed image data is minimized for each horizontal line, the memory capacity can be reduced, and the device can be downsized, and efficient high-precision compression / decompression processing can be performed in a short time. It can be carried out.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image data compression / decompression method and an image data compression / decompression device.

[0002]

2. Description of the Related Art Conventionally, compression / expansion of image data has been performed by a run length method such as EFM (Eight).
t to fourteen modulation)
Various compression / expansion methods are used, and by compressing / expanding image data, it becomes possible to represent image information with a small number of bits. As described above, if the image information can be expressed with a small number of bits, it becomes possible to reduce the memory capacity and shorten the processing time of the image information in the device that processes the image information.

[0003]

The various conventional compression / expansion methods are suitable or unsuitable depending on the image data to be applied. There are various general run length methods and various run length units. The compression rate differs depending on whether the unit is adopted, and it cannot be said that a certain unit is suitable for all image data. In particular, the image data is biased depending on the position on the image, and if the same compression / expansion method is applied to all the image data on the image, a wasteful part is likely to occur in the compression / expansion process. The present invention has been made based on the above-mentioned current situation of compression / expansion of image data, and an object of the present invention is to provide an image data compression / expansion method and an image data compression / expansion device for performing efficient compression / expansion without waste. To provide.

[0004]

The above object is to divide image data into a plurality of pixel groups for each horizontal line, and perform a plurality of predetermined compression processes for each pixel group to obtain the minimum compressed data. This is achieved by providing a compression pattern selection step of selecting a compression pattern and a storage step of storing related data of the compression pattern selected in the compression pattern selection step. Further, specifically, in the selecting step, each pixel group is compared with the immediately preceding pixel group, and if both pixel groups are the same in this comparison, selection processing is not performed, and in the storing step, the immediately preceding pixel group Corresponding numbers of compression patterns are stored, and if both pixel groups are not the same in the above comparison, the storing step stores the compressed data of the compression patterns selected in the selecting step and the corresponding numbers of the compression patterns. be able to. More specifically, it is possible to further include a decompression step of reading the corresponding number of the compression pattern stored in the storage step and performing decompression processing of each pixel group with the corresponding decompression pattern.

On the other hand, the above object is achieved by adopting the configuration of the block diagram of the present invention shown in FIG. 1. The image data 7a obtained from the image 7 is divided into a plurality of pixel groups for each horizontal line, A compression pattern selection unit 5 that performs a plurality of predetermined compression processes for each pixel group and selects the compression pattern 2 that is the minimum compression data, and the related data of the compression pattern selected by the compression pattern selection unit 5 is stored. This is achieved by providing the storage means 1. Further, specifically, it is possible to further provide a decompressing unit 6 that reads the corresponding number 2a of the compression pattern stored in the storage unit 1 and performs the decompression process of each pixel group by the corresponding decompression pattern 3.

[0006]

In the present invention according to the method, as shown in the flowchart of FIG. 2 showing the image data compression processing, in the compression pattern selection step, the input image data is divided into a plurality of pixel groups for each horizontal line, A predetermined plurality of compression processes are performed for each pixel group, a compression pattern that is the minimum compressed data is selected (steps S1 to S3), and the storage process relates the compression patterns selected in the compression pattern selection process. Data is stored (step S
4). If the minimum compression pattern is not selected, the original image data is stored as it is (step S
5). Specifically, in the selecting step, each pixel group is compared with the immediately preceding pixel group, and if both pixel groups are the same in this comparison, the selecting process is not performed, and in the storing step, the compression pattern of the immediately preceding pixel group is performed. If the two pixel groups are not the same in the comparison, the compressed data of the compressed pattern selected in the selection step and the corresponding number of the compressed pattern are stored in the storage step. More specifically, as shown in the flowchart of FIG. 3 showing the image data decompression process of the method of the present invention, in the decompression process, the corresponding numbers of the compression patterns stored in the storage process are read out, and the corresponding decompression patterns are used to read the corresponding numbers. Pixel group expansion processing is performed (steps S6 to S7).

Further, in the present invention according to the above-mentioned apparatus, the compression pattern selection means 5 divides the image data 7a into a plurality of pixel groups for each horizontal line, and a plurality of predetermined compression processes for each pixel group. Then, the compression pattern 2 having the minimum compression data is selected, and the storage unit 1 stores the related data of the compression pattern 2 selected by the compression pattern selection unit 5. Further, specifically, the decompression unit 6 reads the corresponding number 2a of the compression pattern 2 stored in the storage unit 5, and the corresponding decompression pattern 3 performs the decompression process of each pixel group.

[0008]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings based on an image data compression / decompression device. FIG. 4 is an explanatory diagram showing the configuration of the embodiment, and as shown in FIG.
ROM 11, RAM 13 and video display processor (hereinafter referred to as VDP) 14 via U 11 to bus 11.
And a display display 16 and a video RAM (hereinafter referred to as VRAM) 15 are connected to the VDP 14. Here, the CPU 11 has a function of controlling the overall operation of the embodiment including compression / expansion processing, and the ROM 12
The operation program of the embodiment is stored in the RAM 1
3 stores compression pattern data and decompression pattern data of various methods such as run length and EFM, and their corresponding number data. Further, the VDP 14 has a function of controlling the display of the image data on the display display 16, and the VRAM 15 has a function of storing the compressed / decompressed image data and the corresponding number of the corresponding compression / decompression pattern. ..

Next, the processing operation in the embodiment having such a configuration will be described first with respect to image compression processing. FIG. 5 is a flow chart of the compression process of the embodiment, in which one horizontal line of image data is taken out by a command from the CPU 11.
A comparison is made as to whether it is the same as the image data of the immediately preceding horizontal line (steps S10, S11, S12). If both image data are the same in this comparison, the corresponding number (compression number) is set to 0 and step S19 is performed. (Step S1
4). In this case, the VRAM 15 stores the corresponding number of the compression pattern of the image data of the immediately preceding horizontal line corresponding to the horizontal line. If the horizontal 1 line of the image data is not the same as the image data of the previous horizontal line in step S12, the compression method (corresponding number 1 to MAX) in all the compression patterns stored in the RAM 13 is tried.
A compression pattern having the smallest data size of the compression result is searched for (steps S13 to S18). Then, the corresponding number (1 to N) of the compression pattern with the smallest data size of the compression result is
If all the compression patterns are stored in the VRAM 15 and exceed the original size of the image data, the corresponding number -1 is stored (step S19). Then, this process is repeated for all horizontal lines (steps S20, S).
21). Table 2 shows the corresponding numbers (compression numbers), the contents of the compressed data, and the stored data collectively in these cases.

[0010]

[Table 2] Further, when storing in the DRAM 15, as shown in Table 1, a compression number is stored at the head of the storage area, and if the compression number is 1 or more, the image data compressed next to this compression number is stored, and the compression number is -1. When, the original image data is stored, when the compression number is 0, the data is not stored.

[0011]

[Table 1] FIG. 6 is a flowchart of the image expansion processing of the embodiment,
The VDP 14 reads the compression number data at the head of the compressed data, and if the compression number is 0, copies the decompressed data of the previous horizontal line as it is and displays it on the display 16 (steps S31, S32, S33, S37). If the compression number is -1, the original image data is displayed on the display display 16 as it is on the horizontal line (step S).
31, S32, S33, S34, S36). If the compression number is 1 or more, the image data is decompressed by the decompression method of the decompression pattern corresponding to the compression number and displayed on the display 16 (steps S31, S32, S33, S34,
S35). This process is repeated until the display of all horizontal lines is completed (steps S38 and S39).

As described above, according to the embodiment, the optimum compression pattern for the image data of each horizontal line is selected from a plurality of compression patterns and the image data is compressed so that the compressed image data is minimized. It is possible to reduce the storage area, and the processing load at the time of reading is almost the same as the conventional one. In addition, it is possible to easily incorporate various types of compression patterns that will be developed in the future. By performing advanced compression / decompression processing, the processing time is shortened, and image data compression that efficiently and highly accurately performs compression / decompression is performed. A decompression method and apparatus are provided.

[0013]

As described above, according to the present invention, in the compression pattern selecting step, the image data is divided into a plurality of pixel groups for each horizontal line, and a plurality of compression processes predetermined for each pixel group are performed. By selecting the compression pattern that produces the minimum compressed data and storing at least the corresponding number of the compression pattern selected in the compression pattern selection step in the storage step, it is efficient and optimal for image data. It is possible to provide a method for compressing and decompressing image data capable of performing the compression process of (1) in a short time.

Further, according to the present invention, the compression pattern selection means divides the image data into a plurality of pixel groups for each horizontal line, and performs a plurality of predetermined compression processes for each pixel group to obtain the minimum compressed data. Since the storage means stores at least the corresponding number of the compression pattern selected by the compression pattern selection means, the image data is always compressed for each horizontal line so that the compressed image data is minimized. Thus, the memory capacity can be reduced, the device can be downsized, and an image data compression / decompression device capable of efficiently performing highly accurate compression processing in a short time can be provided.

[Brief description of drawings]

FIG. 1 is a block diagram showing a configuration of the present invention.

FIG. 2 is a flowchart showing a compression process of image data according to the present invention.

FIG. 3 is a flowchart showing a decompression process of image data according to the present invention.

FIG. 4 is an explanatory diagram showing a configuration of an embodiment of the present invention.

FIG. 5 is a flowchart showing image compression processing according to an embodiment of the present invention.

FIG. 6 is a flowchart showing an image expansion process according to an embodiment of the present invention.

[Explanation of symbols]

 1 Storage Means 2 Compression Pattern 2a Corresponding Number 3 Expansion Pattern 5 Compression Pattern Selection Means 6 Expansion Means 11 CPU 12 ROM 13 RAM 14 Video Display Processor 15 Video RAM 16 Display Display

Claims (5)

[Claims] 1. A compression pattern selection for dividing image data into a plurality of pixel groups for each horizontal line, performing a plurality of predetermined compression processes for each pixel group, and selecting a compression pattern that provides the minimum compressed data. A method for compressing and decompressing image data, comprising: a step; and a storage step of storing related data of the compression pattern selected in the compression pattern selection step. 2. In the selecting step, each pixel group is compared with the immediately preceding pixel group, and if both pixel groups are the same in this comparison, the selection processing is not performed, and in the storing step, the compression pattern of the immediately preceding pixel group is performed. Is stored, and if both pixel groups are not the same in the above comparison, the storage step stores the compressed data of the compression pattern selected in the selection step and the corresponding number of the compression pattern. The method of compressing and expanding image data according to claim 1, wherein. 3. The method according to claim 1, further comprising a decompression step of reading the corresponding number of the compression pattern stored in the storage step and performing decompression processing of each pixel group with the corresponding decompression pattern. Image data compression and decompression method. 4. A compression pattern selection for dividing image data into a plurality of pixel groups for each horizontal line, performing a plurality of predetermined compression processes for each pixel group, and selecting a compression pattern that provides the minimum compressed data. An image data compression / decompression device comprising: means for storing image data related to the compression pattern selected by the compression pattern selection means. 5. The image data according to claim 4, further comprising a decompressing unit that reads out the corresponding number of the compression pattern stored in the storage unit and decompresses each pixel group with the corresponding decompression pattern. Compression / expansion device.