JPH0492572A - Data compressing device - Google Patents

Abstract

PURPOSE:To always obtain a high data compression ratio by comparing the amount of data of encoded data obtained by a reverse encoding means with those of the encoded data obtained by a normal encoding means, selecting one encoded data whose amount of data is small, and outputting them. CONSTITUTION:Inputted binarization data are encoded as it is, and at the same time the binarization data whose bit value is reversed is encoded. Then, the amounts of data of the two obtained encoded data are compared, and one encoded data whose amount of data are small is outputted. Thus, a provided amount of data comparing and selecting circuit 5 compares the amounts of data of encoded picture information outputted from each of encoding circuits 3 and 4, and takes away one encoded data whose amount of data are small. Then, an output format preparing means 6 adds various codes to the encoded data in order to prepare a data format format for a facsimile transmission. Thus, the constant high data compression ratio can be obtained in spite of the bit value of the binarization data.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a data compression device suitable for data compression of image information.

[Prior Art] In general, facsimile machines comply with CCITT Recommendation T, 4.
Or in accordance with T, 6, M H (Modified l
luffman), M R (Modified REA
D) or MMR (Modified MR) encoding methods are used to transmit image information.

Each of these encoding methods basically performs encoding by replacing the run length of black and white pixels with a Huffman code.

In CCITT's Huffman codes for facsimile, each code is defined for each run length of black pixels and white pixels.

FIG. 5(a) shows the number of bits of the Huffman code for each run length of black pixels, and FIG. 5(b) shows the number of bits of the same code for each run length of white pixels.

In either case, as the run length increases, the number of code bits also increases. However, when the run length exceeds a certain value, the number of sign bits is larger for black pixels than for white pixels.

[Problems to be Solved by the Invention] Therefore, when encoding an image with many consecutive black pixels, the data compression rate is lower than when encoding an image with similar consecutive white pixels. . For this reason, when a facsimile device transmits a document image with many black areas, it takes longer to communicate than a document image with many white areas.

In this way, conventionally, when compressing data.

Even if the run length of the original data is the same, there is an inconvenience that the data compression rate changes depending on whether the data bit is "1" or rQJ.

SUMMARY OF THE INVENTION An object of the present invention is to provide a data compression device that can eliminate the above-mentioned disadvantages and can always obtain a high data compression rate regardless of the bit value of the data.

[Means for Solving the Problems] To this end, the present invention encodes input binary data as it is, and at the same time encodes binary data with bit values inverted, thereby generating two resulting encoded data. This feature is characterized in that the amounts of data are compared, and the encoded data with the smaller amount of data is output.

[Operation] This makes it possible to obtain a constant data compression rate regardless of the bit value of binary data.

[Embodiments] Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings.

FIG. 1 shows a block diagram of a data compression device according to an embodiment of the present invention. In the figure, an input circuit 1 inputs binary image information line by line, and a bit inversion circuit 2 inverts black pixels and white pixels, that is, "1" and "0" of the input image information. It is something. The encoding circuits 3 and 4 encode input image information using various methods such as MH, MR, and MMR, respectively.

The data amount comparison/selection circuit 5 compares the amount of encoded image information output from the encoding circuits 3 and 4, and extracts the one with the smaller amount of data. The output format forming circuit 6 adds various codes to the encoded data to form a data format for facsimile transmission.

With the above configuration, it is assumed that the data compression apparatus of this embodiment is installed in a facsimile machine.

This data compression device is activated when a document image reading operation is started during transmission by a facsimile device.

When the data compression device is activated, as shown in Figure 2,
The input circuit 1 sequentially inputs image information read from a document line by line and outputs it to the encoding circuit 3 and the bit inverting circuit 2 (process 101).

The encoding circuit 3 encodes the image information as it is. Further, the bit inversion circuit 2 inverts the bits of the image information, and the encoding circuit 4 encodes the bit-inverted image information (processing] 02). The data amount comparison/selection circuit 5 is
The encoded image information for I lines output from the encoding circuits 3 and 4 is inputted, respectively, and the data amounts of the two are compared. Then, the encoded image information having the smaller amount of data and information indicating which image information it is are outputted to the output format forming circuit 6 (processing 103).

The output format forming circuit 6 adds EO to the input encoded image information, as shown in FIG.
The L code and a 1-bit identification code X indicating whether or not the image information is bit-inverted are added to form transmission data in a fixed format and output (process 104).

The output transmission data is transmitted by a transmission section (not shown) of the facsimile machine.

After this, the process 105 checks the presence or absence of image information for the next line. If there is one-stroke information (Y in process 105), repeats the encoding process for each line in the same way (proceeds to process 101). When the information runs out (N in process 105),
The above encoding process ends.

In addition, on the receiving side, when the above transmission data is received, the EO
The data of each line is extracted by identifying the L code. Next, the image information in the data is decoded, and the identification code X of the data is determined. here,
If the identification code does not indicate bit inversion, the image information obtained by the above decoding is output as is. On the other hand, if bit inversion is indicated, the image information is bit inverted and then output.

As described above, in this embodiment, the original image information of each line and the black and white inverted image information are encoded, and the one with the smaller amount of data is extracted.

As a result, high data compression rates can be obtained for both original images that have many consecutive black pixels and original images that have many consecutive white pixels.

Incidentally, in the above-described embodiment, the data amount of encoded image information is determined on a line-by-line basis, but it may be determined on a page-by-page basis.

Figure 4 shows a block configuration diagram in this case.
The difference from FIG. 1 is that a page memory 7.8 for temporarily storing encoded image information for one page is newly provided.

With this configuration, the input circuit 1, the bit inverting circuit 2, and the encoding circuits 3 and 4 input image information line by line in the Jllffllff format, as in the previous embodiment. At this time, the page memory 7.8 stores one page of encoded and output image information.

The data amount comparison/selection circuit 5 includes one of the page memories 7 and 8.
The data amount of encoded image information for one page is compared and the smaller one is extracted. Then, the output format forming circuit 6 adds one identification code to the image information for one page, indicating whether or not the image information is bit-inverted.

As a result, only one identification code is required per page, so the amount of output data can be reduced.

Note that in the above embodiment, the data amount of encoded image information is
I explained how to judge by line and page, but
In addition, it is possible to make the determination in units of a certain line or in units of multiple pages.

Furthermore, although two encoding circuits are provided, it is possible to reduce the number of encoding circuits to one by separately performing encoding of 1-element image information and encoding of bit-inverted image information. .

Further, in each of the above-described embodiments, a case has been described in which image information is encoded by a facsimile machine, but the present invention is applicable not only to image information but also to run-length encoding of various data such as audio data. It can be applied to

[Effects of the Invention] As described above, according to the present invention, two
The value data is encoded as is, and the bits are inverted and encoded to increase the power of the encoded data, which has a smaller amount of data, so a constant high data compression rate can be achieved regardless of the bit value of the binary data. be able to obtain it.

[Brief explanation of drawings]

FIG. 1 is a block configuration diagram of a data compression device according to an embodiment of the present invention, FIG. 2 is an operation flowchart of encoding processing, FIG. 3 is an explanatory diagram of the data format of output data, and FIG. FIGS. 5(a) and 5(b), which are block configuration diagrams of a data compression apparatus showing another embodiment, are graphs showing the number of bits of a Huffman code for each run length. 1... Input circuit, 2... Bit inversion circuit, 3, 4...
... Encoding circuit, 5... Data amount comparison/selection circuit, 6
... Output format forming circuit, 7, 8... Page memory.

Claims (2)

[Claims] (1) In a data compression device that encodes binary data by sequentially replacing each run length with each code, but in which the number of bits of each code differs depending on the bit value of the binary data even for the same run length, An input means for inputting a fixed amount of binary data, a normal encoding means for encoding the input binary data as it is, a bit inversion means for inverting each bit value of the input binary data, and a bit inversion means for inverting each bit value of the input binary data. an inverse encoding means for encoding value data; a data amount comparison means for comparing the amount of encoded data obtained by the inverse encoding means and the encoded data obtained by the normal encoding means; 1. A data compression device comprising: data selection means for selecting and outputting encoded data having a smaller amount of data. 2. The data compression apparatus according to claim 1, further comprising an output format forming means for adding an identification code to the output encoded data to indicate whether or not the data is bit-inverted data.