JPH0695728B2 - Image data compression / reproduction device - Google Patents

Description

TECHNICAL FIELD The present invention relates to an image data compression / reproduction device.

2. Description of the Related Art Generally, in an image data processing system, it is often necessary to store (store) data as system resources are shared. However, since the image data has a large amount of information, it is common to use a method of compressing and storing the data.
The MH (Modifies Huffman) method, which is one-dimensional compression, and the MR (Modifies Read) method, which is two-dimensional compression, are used. In the MH method, the length (run length) RL in which black or white pixels continue in the scanning line direction is a 64-base system, that is, RL = (64M) +
It is represented by (T), Huffman code words are assigned to (64M) and (T), and different code words are assigned to white run and black run having different statistical properties. 91 (= 1728 words required)
64 + 27) words, but since it is one-dimensional compression, the compression rate does not reach that of the MR method, which is two-dimensional compression.

Also, the MR method focuses on the pixels (change pixels) on the black-and-white boundary between the coded scan line (current scan line) and the reference scan line immediately above, and the position of each change pixel on the coded scan line is encoded and scanned. A code word of pass mode, vertical mode, or horizontal mode is assigned and encoded by referring to a corresponding reference change pixel on a line or a reference scanning line, and significant data compression is performed as compared with one-dimensional encoding. You can By the way, since the two-dimensional encoding method such as the MR method is based on the scanning line immediately above, if an error occurs, it will spread to subsequent scanning lines one after another. Therefore, in order to prevent the spread of errors, K
Although one scanning line is used for one-dimensional encoding for each scanning line, in the conventional two-dimensional compression method, the K parameter indicating the one-dimensional encoding period is 2 in the standard mode or 4 in the high quality mode. Is standardized and fixed, and a one-dimensional compression section having a low compression rate appears every 2 or 4 lines, and a high compression rate cannot be obtained as a whole.

Purpose The present invention has been made in view of the actual situation as described above,
The present invention has been made for the purpose of providing an image data compression / reproduction device capable of obtaining a high compression rate.

Structure In order to achieve the above object, the present invention (1) is a data compression / reproduction unit that normally performs two-dimensional compression and performs one-dimensional compression for every K lines, and the line data has a uniform level of the same color. A uniform level detecting means for determining whether or not,
The data compression / reproduction means is configured to perform two-dimensional compression regardless of the value of the K parameter while the uniform level detection means determines that the line data has the uniform level of the same color. In addition, (2), the compression reproduction means is provided with an input / output buffer section. Hereinafter, description will be made based on examples.

FIG. 2 is a diagram showing a basic configuration of a data processing system having an image data storage function according to the present invention. Reference numeral 1 is a CPU connected to a terminal T or the like. 2 is a memory for data storage, 3
Is a program memory, 4 is a bit map memory, 5 is a compression reproducing apparatus (DCR) according to the present invention, 6 is an input interface for inputting data through the scanner 7, 8 is an output interface for outputting data to the printer 9, and 10 is for communication. The interface, 1 is a CRT, and 12 is a keyboard input device, which communicate via a system bus 13.

In FIG. 2, the image data is the input interface 6
Through the scanner 7 or through another interface through the communication interface 10. This image data is expanded on the bitmap memory 4 and displayed on the CRT 11. The operator edits based on the display contents of the CRT. The edited result may be stored in the storage memory 2 for a later date. At that time, the image data is compressed via the compression / reproduction device 5, and the amount of data is reduced. In this way, the compression / reproduction device 5 compresses the image data processed in the system and reproduces the stored compressed data.

By the way, the line data read by the scanner has a characteristic that there are many lines of uniform level (all white or all black) and they are continuously generated, and the present invention makes use of the feature of this line data. As long as the same color data of 1 continues, two-dimensional compression is to be continued regardless of the value of the K parameter indicating the cycle of one-dimensional encoding. Thus, according to the present invention, when the error spread line is increased due to continuous two-dimensional compression, the "all white line" or "all black line" is not a normal data line but a "margin part". It is based on the fact that it cannot be fatal because it is a "real area".

FIG. 1 is a block diagram of a data compression / reproduction device that realizes the data compression / reproduction method according to the present invention. Reference numeral 20 denotes a data compression / reproduction device, which is used for efficient use of the system bus 21. With this, data for one line is collectively transferred. The compression / playback unit 22
It has hardware for two-dimensional compression (MR method). Then, the input data from the system bus is detected by the uniform level detection circuit 25 as "all white line" or "all black line", and the flag 27 in the controller 26 is "all white line" or "all black line". Issue a flag signal of. And 2 while there is a flag output of "all white line" or "all black line"
The dimension data compression mode is continued.

FIG. 3 is a diagram showing an example of the uniform level detecting circuit 25 of FIG. 1, and a black-and-white data signal (white: 0, black: 1) for one line from the data bus 31 for inputting data to the input buffer section 30. But OR
It is input to the JK flip-flop 33 via the gate 32. If the Q output is 0, it is detected that it is "all white". The detection of all black can be easily configured in the same manner.
Reference numeral 34 is a strobe signal generation circuit for writing data in the input buffer 30.

FIG. 4 is a flowchart showing a data compression / reproduction method according to the present invention. First, in the case of two-dimensional compression, the K parameter is determined, the K counter is set to 1, and the data for one line is DCR (compression / reproduction device). Transfer to. the system,
The value of K is checked, and if it is the first line, one-dimensional compression is performed, and when it is completed, 1 is added to the value of K. Next, the system checks the contents of the K counter, performs two-dimensional compression until the number of K lines is reached, and increments the contents of the K counter by 1 each time the data compression processing for one line is completed. When the line reaches the Kth line, the uniform level detection circuit determines whether it is an all-white line or an all-black line, and if it is a uniform level, the two-dimensional compression is continued and the contents of the K counter are not updated. If the level is not uniform, the contents of the K counter are updated when the two-dimensional compression of the line is completed, and the data compression from the first line is performed again, and this operation is continued thereafter. Thus, as long as the line data has a uniform level such as all white or all black, the two-dimensional compression with a high compression rate is continued even if the scanning reaches the Kth line. In the above example, the system controls the K count value and the compression method by the K parameter, but the management of the K count value and the determination of the compression method may be left to the compression reproducing device. . In that case, the system sends the K parameter to the compression reproducing apparatus at the start of data compression, and receives a flag indicating whether the compression method is one-dimensional or two-dimensional when receiving the processed data. In this case, the system does not have to receive a uniform level of flags from the compression player.

Effect As is clear from the above description, according to the present invention, the two-dimensional compression is continued as long as the line data is at a uniform level without being restricted by the fixed K parameter as in the conventional case.
As for hardware, it is possible to realize data compression with a high compression rate simply by adding a uniform level detection circuit having a simple configuration.

[Brief description of drawings]

FIG. 1 is a block diagram of a data compression / reproduction device according to the present invention, FIG. 2 is a basic configuration diagram of a data processing system according to the present invention, FIG. 3 is a uniform level detection circuit diagram, and FIG.
It is a flowchart. 20 …… Compressor / reproducer, 21 …… System bus, 22 …… Compressor / reproducer, 23 …… Input buffer, 24 …… Output buffer, 25,30 …… Uniform level detection circuit, 26 …… Controller, 27 ...... Flag, 31 …… Data bus, 33 …… F / F circuit, 34 …… Strobe generation circuit.

Claims (2)

[Claims] 1. Usually, two-dimensional compression is performed, and one is performed for each K line.
The data compression / reproduction means for performing dimension compression and the uniform level detection means for determining whether or not the line data have the same color uniform level, and the uniform level detection if the line data have the same color uniform level The image data compression / reproduction device, wherein the data compression / reproduction means is configured to perform two-dimensional compression regardless of the value of the K parameter while the determination is made by the means. 2. The image data compression / reproduction device according to claim 1, wherein the compression / reproduction means includes an input / output buffer section.