JPH044673A - Encoding system for picture data - Google Patents

Abstract

PURPOSE:To reduce a storage capacity required for an encoding conversion table to 1/2 or below by using sa same encoding conversion table needing less code word bit number so as to apply encoding and compression to a white run length data and a black run length of a binarized picture data. CONSTITUTION:Both a white run length data and a black run length of a binarized picture data obtained by scanning a character or a picture are converted by using a white run length data encoding conversion table. Thus, the encoded bit number for the black run length data is reduced. Then a bit number after the conversion is reduced and the compression efficiency is improved. Moreover, one encoding conversion table for the white run length data is enough for the encoding and the storage capacity required for the encoding conversion table of a storage means is reduced to 1/2 or below in comparison with that of a conventional system.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to an image data encoding method used in facsimile machines and the like.

(Prior art) MH encoding method used in facsimile machines, etc.
MH encoding line (one-dimensional compression line) of R encoding method
In this method, white run length data and black run length data of binary image data obtained by scanning characters and images are encoded and compressed using separate encoding conversion tables.

(Problem to be solved by the invention) However, the MH encoding method (one-dimensional compression method) does not compress data when there are many inversions of black and white on the scanning line, such as halftone data, and conversely, the amount of data There was a problem in that the number of transmission times increased and the transmission time became longer.

Furthermore, it is necessary to separately prepare encoding conversion tables for encoding white run length data and encoding black run length data, which poses the problem of increasing the storage capacity of the storage means.

An object of the present invention is to provide an image data encoding method that solves the above problems by encoding white run length data and black run length data using the same encoding conversion table.

(Means for Solving the Problems) The image data encoding method of the present invention converts binary image data obtained by scanning characters and images into the same encoding conversion for both white run length data and black run length data. This method is characterized by performing coded compression using a table.

Further, the encoding conversion table may be formed using the smaller number of code words between the number of bits of a code word for white run length data and the number of bits of a code word for black run length data.

(Function) In the image data encoding method of the present invention configured as described above, both the white run length data and the black run length data of the binary image data obtained by scanning characters and images have the same code. It is encoded and compressed by using an encoding conversion table.

Therefore, only one encoding conversion table is required, and the storage capacity of the conversion table storage portion of the storage means in which the encoding conversion table is stored can be reduced to 1/2 of that of the conventional system.

Furthermore, if the encoding conversion table is formed using the smaller number of bits of the codeword for the white run length data and the bit number of the codeword for the black run length data, the compression efficiency will be improved.

(Example) The present invention will be explained below with reference to Examples.

FIG. 1 is a schematic diagram showing an example of encoding compression according to an embodiment of the present invention.

In the encoding method of an embodiment of the present invention, both black run length data and white run length data of binary image data obtained by scanning characters and images are processed using an encoding conversion table for white run length data. Convert.

First, FIGS. 2 and 3 show coding conversion tables for terminating codes and makeup codes for white run length data and black run length data in the MH encoding system recommended by CCITT.

As can be seen from this encoding conversion table, except when the black run length data is 1 to 4 bits, the code length is the same as the black run length and white run length, or the black run length is longer than the white run length. . Also, normal M
In the H encoding method, it is determined that the data always starts with own run length data, and that white run length data and black run length data come alternately.

For example, as shown in FIG. 1(a), the binary image data obtained by scanning characters and images consists of 10-bit white run length data (self-portrait signal portion Wl) and 10-bit black run length data (
Taking as an example the case of a picture signal that includes 27 bits of black picture signal part B2, 50 bits of white run length data (self picture signal part W2), and 40 bits of black run length data (black picture signal part B), MH encoding is performed. When the white run length data is converted using the white run length encoding conversion table of the system, and the black run and length data are converted using the black run length encoding conversion table of the system, as shown in FIG. ” ,+oo.

011001011”, +01010011-1”
000001101100” 4. m conversion is performed. Therefore, the total number of encoded bits is 37 bits.

However, in the encoding method according to the embodiment of the present invention, both the black run length data and the white run length data are converted using the encoding conversion table for the white run length data. Therefore, in the case of the above-described binarized image data, '0011°, +
0100100”,”01010011-,+
00101001°, and the number of coded bits is the same for white run length data, but the number of coded bits decreases for black run length data, and the number of coded bits is reduced for black run length data. The total is 28 bits. As a result, the number of bits after conversion is reduced by 9 bits in this example.

Therefore, the number of bits after conversion can be reduced, and compression efficiency can be increased. Furthermore, the encoding conversion table may be formed using the smaller number of bits of the codeword for the white run length data and the bit number of the codeword for the black run length data, which improves the compression efficiency. can be improved.

In addition, the encoding conversion table can be used as the encoding conversion table for the white run length data, and the storage capacity required for the encoding conversion table in the storage means is reduced to less than 1/2 that of the conventional one.

(Effects of the Invention) As explained above, according to the present invention, the binary image data obtained by scanning characters and images is converted into white run length data and black run length data, whichever code word has a smaller number of bits. Since encoding and compression are performed using the same encoding conversion table, the storage capacity required for the encoding conversion table in the storage means can be reduced to less than 1/2 of that of the conventional method. .

Since the encoding conversion table is formed using the smaller number of bits of the codeword for the white run length data and the bit number of the codeword for the black run length data, the compression efficiency by encoding can also be improved.

[Brief explanation of the drawing]

FIG. 1 is a schematic diagram showing an example of encoding and compression according to an embodiment of the present invention. FIGS. 2 and 3 are diagrams showing coding conversion tables for terminating codes and makeup codes for white run length data and black run length data in the MH encoding method recommended by CCITT. Bo, B21, B, ---black image signal part, W,, w2,
W3...White image signal part.

Claims (2)

[Claims] (1) Binarized image data obtained by scanning characters and images is encoded and compressed using the same encoding conversion table for both white run length data and black run length data, whichever has the smaller number of bits in the code word. An image data encoding method characterized by: (2) The encoding conversion table is characterized in that it is an encoding conversion table formed from the smaller number of codewords between the number of bits of a codeword for white run length data and the number of bits of a codeword for black run length data. The image data encoding method according to claim 1.