JPH05304611A - Compression and expansion system for color image data - Google Patents

Abstract

PURPOSE:To improve the compressibility of color image data in a picture processor which processes the color image by dividing it into original color pictures of each three original color. CONSTITUTION:This system is composed of picture memories 2-4 for each original color, a latch circuit 5 which rearranging the binary information of three original colors by picking up the picture information of each original color in a horizontal line direction by every picture element, a line buffer 6 which stores the output information of the latch circuit 5, a compressor 7 which compresses the color image data stored in the line buffer 6, and an expander 8 which expands the color image data compressed by the compressor 7.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a compression / expansion system for color image data.

[0002]

As is well known, a color image is formed by a pattern of colored pixels and colorless pixels. Generally, a plurality of colored pixels or colorless pixels are continuous.
Therefore, color image data in which one pixel is represented by 1 bit often has a bit pattern in which a plurality of "0" s or "1" s are consecutive. For serial processing of such bit-patterned color image data, for example, in the case of data transmission, a Huffman code or the like that assigns a short code to the rank of a bit pattern with a high appearance probability is adopted. Then, it is known to speed up the process by compressing the data.

Data compression is performed by encoding each time different binary information appears. The compressed color image data is decompressed and decompressed after serial processing.

In the conventional compression / expansion method of this kind of color image data, an image memory for each three primary colors that stores each pixel forming a primary color image as color image data expressed by binary information, and the image memory are stored. And a decompressor for decompressing the color image data compressed by the compressor. The color image data is compressed for each of the three primary color image data read from the image memory. The compressed color image data is also expanded as it is for each of the three primary color image data.

[0005]

In such a prior art, since no processing operation is performed on the color image data of all three primary colors at the time of compression and therefore at the time of expansion, the compression rate is the bit pattern of the color image data. It has the disadvantage that it is only determined by the code used for compression.

[0006]

A color image data compression / expansion method according to the present invention comprises an image memory for each of the three primary colors for storing each pixel constituting the primary color image as color image data expressed by binary information, and A latch circuit for retrieving the binary information of the three primary colors in the horizontal line by picking up pixel information for each primary color one pixel at a time, a line buffer for storing output information of the latch circuit, and a command from a processing unit in the image processing apparatus. In response to the command from the processing unit, and a decompressor for decompressing the color image data stored in the line buffer in response to a command from the processing unit. It

[0007]

The present invention will be described in detail with reference to the drawings.

FIG. 1 is a block diagram showing an embodiment of the present invention. In this embodiment, a device for transmitting and receiving color image data having three primary colors of red, green and blue to and from a partner device (not shown) via a data transmission line under the control of the processing unit 1. Shown, 3 image memories 2, 3 and 4
A latch circuit 5, a line buffer 6 and a compressor 7,
It is composed of an expander 8 and a selector 9. The data transmission line is connected via a modem to the end of a line extending to the right of the compressor 7 and the decompressor 8. The partner device also includes the compressor 7 and the expander 8.

The image memories 2, 3 and 4 are red,
1 color image data for green and blue primary color images
Only the main scanning direction (from left to right) is stored for each address. The color image data from the processing unit 1 responds to the read / write signal 11 output by the processing unit 1 and the select signal 13 output by the selector 9 decoding the color designation signal 12 output by the processing unit 1, and the image memory 2 , 3 and 4, respectively, are divided into red, green and blue read / write data lines 14
Are sequentially written via. The write address is common to all the image memories 2, 3, and 4, and the processing unit 1 supplies it via the address line.

The stored contents of the image memories 2, 3 and 4 thus written are sequentially read by the processing unit 1 via the read / write data line 14 in response to the read / write signal 11 and the select signal 13. You can The selector 9 sequentially outputs the select signal 13 for the address supplied by the processing unit 1 via the address line, and reads the image memories 2, 3 and 4 to the latch circuit 5. The latch circuit 5 transfers the data on the read line 15 to the image memories 2, 3, 4
The pixels are rearranged one by one in this order and stored in the line buffer 6. The compressor 7 takes out the data from the line buffer 6 and compresses it, and after compression, it is transmitted bit serially through the data transmission line.

Next, when receiving the compressed color image data transmitted from the partner device, the decompressor 8 decompresses the compressed data and stores it in the line buffer 6. The latch circuit 5 sequentially stores the contents of the line buffer 6 in the image memories 2, 3 and 4 pixel by pixel.
The decompressor decompresses the input compressed color image data from the other device one by one as described above and stores it in the line buffer, and the image memories 2, 3 for each one pixel are stored.
4 is written via the write data line 16. At this time, the image memories 2, 3 and 4 are sequentially selected by the select signal 13 sequentially output from the selector 9 with respect to the same address supplied by the processing unit 1.

[0012]

According to the present invention, since the bit pattern of color image data can be made to have a low frequency of binary information change, the compression rate of color image data for a natural color image can be improved.

[Brief description of drawings]

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

[Explanation of symbols]

 1 Processing Unit 2, 3, 4 Image Memory 5 Latch Circuit 6 Line Buffer 7 Compressor 8 Expander 9 Selector 11 Read / Write Signal 12 Color Designating Signal 13 Select Signal 14 Read / Write Data Line 15 Read Data Line 16 Write Data Line 17 Data Transmission Command

Claims (1)

[Claims] 1. An image memory for each of the three primary colors, which stores each pixel constituting the primary color image as color image data expressed by binary information, and binary information for the three primary colors, in which pixel information for each primary color is provided in the horizontal line direction. A latch circuit that takes out and rearranges one pixel at a time, a line buffer that stores output information of the latch circuit, and a compression that compresses color image data stored in the line buffer in response to a command from a processing unit in the image processing apparatus. And a decompressor for decompressing the color image data compressed by the compressor in response to a command from the processing unit.