JPH0659857A - Data compressor - Google Patents

Abstract

PURPOSE:To realize a high compression rate by employing a multidimensional space for a character storage section so as to give a directivity to coincident character strings thereby generating much more codes in the same size of the character storage section. CONSTITUTION:A character string coincidence discrimination section 12 discriminates a position, a length and a direction of a Japanese word character group in the inside of a character storage section 11 coincident with an inputted Japanese character string 16 longest from the head thereof and outputs the discriminated result. A coding section 13 encodes an output of the character string coincidence discrimination section 12 into a binary number. The Huffman coding may be employed for the coding. The data compression is realized by the coding. A 1st decoding section 14 receives a coded character string 17. The 1st decoding section 14 decodes the coded character string 17 into the position, the length and the direction of the Japanese character group in the inside of the character storage section 11. A 2nd decoding section 15 decodes the decoded character string from the character storage section 11 based on the position, the length and the direction of the Japanese character group in the inside of the character storage section 11.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a data compression apparatus for encoding an input character string into an encoded character string and decoding the encoded character string into an input character string.

[0002]

2. Description of the Related Art In recent years, a data compression encoding / decoding apparatus has been used because it is necessary to process a large amount of information. As the compression encoding / decoding device, the LZSS method, the LZW method (“Mandatory and data compression algorithms and practices”, The Bas
ic, March 1989, p1-65). FIG. 5 shows an example of a block diagram of these devices, and their operation will be described step by step. In these devices, the character string coincidence determination unit 52 compares the input character string 57 that has been input with the second character string inside the character storage unit 51, and the encoding unit 53 outputs the comparison result to the encoded character 58. Encode.
Each time the encoded characters 58 are encoded, the character storage unit updating unit 56 updates the second character string inside the character storage unit 51 using the input character string 57 and the comparison result. The first decoding unit 54 stores the encoded characters 58 in the character storage unit 5.
The second character string in 1 and the input character string 57 are decoded by the comparison result obtained by the character string matching determination unit 52, and the second decoding unit 55 decodes the comparison result into the decoded character string 59. Decrypt to. Each time each encoded character 58 is decoded, the character storage unit updating unit 56 updates the second character string inside the character storage unit 51 using the comparison result and the decoded character string 58.

[0003]

However, in order to realize a high compression rate by the above processing, there is a problem that a large-capacity character storage unit is required. In order to solve the above problems, the present invention uses a character storage unit as a multidimensional space, refers to a group of characters for coincidence reference in a multidimensional direction, and in a character storage unit of the same size, for a character string to be compressed, An object of the present invention is to provide a data compression device that can realize a high compression rate by replacing more types of character strings.

[0004]

A data compression apparatus according to the present invention includes a character storage unit for storing a character group, a position, a length and a direction in which an input character string and the character group in the character storage unit match each other. A character string matching determination unit that determines, and an encoding unit that encodes the character string position, length, and direction into an encoded character string,
A first decoding unit for decoding the encoded character string in the position, length and direction of the character group inside the character storage unit; and decoding from the position, length and direction of the character group in the character storage unit A second decoding unit for decoding into a character string is provided.

[0005]

The present invention makes it possible to perform encoding / decoding at a high compression rate by making the character storage unit multidimensional.

[0006]

DESCRIPTION OF THE PREFERRED EMBODIMENTS A data compression apparatus according to an embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 shows the configuration of a data compression apparatus according to an embodiment of the present invention. In FIG. 1, 11 is a character storage unit that stores a character group, 12 is a character string that matches the input character string and the start position where the character groups inside the character storage unit 11 match, and the character length that matches Of the character string in the character storage unit 11, 13 is an encoding unit for encoding the position, length and direction of the character group in the character storage unit 11, and 14 is a character group in the character storage unit 11 for the encoded character string. , A second decoding unit 15 for decoding the position, length and direction of the character group in the character storage unit 11 into a character string before being encoded, 16 Is an input character string to be encoded, 17 is an encoded coded character string, and 18 is the input character string decoded from the coded character string.

In the data compression apparatus configured as described above, a specific example is shown in FIG. 2 for encoding the input Japanese character string and in FIG. 4 for decoding the encoded character string. Will be described with reference to FIG.

FIG. 2 is a flow chart showing the operation of the data compression apparatus shown in FIG. 1 at the time of encoding.

First, the input Japanese character string 16 is input to the character string matching determination unit 12 (201). The character string match determination unit 12 determines the length of the input Japanese character string 16 and the direction in which the character and the start position of the Japanese character group in the character storage unit 11 that match the longest match. A determination is made (202). FIG. 3B shows the input character string 16,
FIG. 3A is an example of a character group inside the character storage unit 11.
The character group inside the character storage unit 11 stores a series of characters that appear frequently. The input character string “Ignored while looking” is the character position (4, 4) of the character group in the character storage unit 11.
4), the character matching length is 2, and the character matching direction is + x. The character string matching determination unit 12 outputs this information. Next, the character string match determination unit 12 determines the remaining "Inaga" of the input character string 16 in the same manner as the character position (14,
3), the character matching length 3 and the character matching direction -y are output. Further, the character string matching determination unit 12 compares “ra” with the character group inside the character storage unit 11. However, since "ra" does not exist in the character group, the information that it does not exist and the character code of "ra" (for example, the JIS code) are output. The character string matching determination unit 12 outputs the two matching positions of “ignored” and “done”, the length, and the direction in the same manner for the remaining “ignored”. FIG. 3D summarizes the output of the character string match determination unit 12 for the input character string “Ignored while looking”.

The encoding unit 13 encodes the output of the character string matching determination unit 12 (205, 206, 207). Figure 3
(C) is an example of a code table that encodes a character position, a character matching length, and a character matching direction.
It represents that the Y coordinate is 3 bits, the character length is 3 bits, and the direction is 2 bits.

In the example of FIG. 3, the encoding unit 13 outputs the first output of the character string match determination unit 12, the character position (44, 4), the character match length 2, and the character direction + X based on each code table.
It is encoded to 001000. The rest is also output by the same procedure, but for the character "ra" that does not exist in the character storage unit, a code 11111111 expressing that it does not exist.
Character code of 1111 and "ra" (eg JIS code)
Is output as a code (208, 209).

Generally, one kanji character is represented by 16 bits. As a result of the above encoding, the input character "Ignored while looking" was encoded and compressed from 160 bits to 76 bits. In particular, the fact that "Inaga" could be encoded in 12 bits is an effect of the two-dimensional character storage unit.

Further, by using Huffman coding for this coding, it is possible to further compress the coded characters.

FIG. 4 is a flow chart showing the decoding operation of the data compression apparatus shown in FIG.

First, the encoded coded character string 17 is input to the first decoding unit 14 (41). First decryption unit 1
4 decodes the encoded character string 17 in the head position, length and direction of the Japanese character group in the character storage unit 11 (44, 4).
5,46). The character position is decoded from the first 4 bits and the next 3 bits of the 12-bit encoded character string 17 of FIG. 3 based on the code table (33). Decode the length from the next 3 bits and the direction from the remaining 2 bits. However,
If the 12 bits are 111111111111, the character code itself is stored next, and it is extracted (48).

The second decoding unit 15 uses the position, length and direction of the Japanese character group inside the character storage unit 11 decoded by the first decoding unit 14 to input the input character string from the character storage unit 11. Decrypt (47). In the example of FIG. 3, character positions (4,
4) Decode "look" from length 2, direction + x. Follow the same procedure to decode the remaining characters, but if there is an output from the first decoding unit that is a character that does not exist in the character group, the output sent next is the character code. Output as is.

In the embodiment, the input character string is Japanese, but the same effect can be obtained for other languages such as English and a digital numerical value sequence in which pixel information of an image is arranged in series.

Furthermore, in the embodiment, the character storage unit is made into a two-dimensional structure, but by making it into a three-dimensional structure and a four-dimensional structure, a high compression rate can be realized.

Further, in the embodiment, the character group inside the character storage unit is fixed, but it may be sequentially updated at the time of compression.

[0021]

As described above, the data compression apparatus of the present invention has a character storage unit for storing a character group, a position, a length, and a direction in which an input character string and the character group in the character storage unit match each other. A character string matching determination unit, an encoding unit that encodes the position, length, and direction of the character group into an encoded character string, and the encoded character string is the position of the character group inside the character storage unit. By providing a first decoding unit for decoding in the length and direction and a second decoding unit for decoding the position, length and direction of the character group in the character storage unit into a decoded character string, It enables encoding and decoding at a compression rate.

Further, by using Huffman coding in the coding unit and Huffman decoding in the first decoding unit, it is possible to realize a higher compression ratio of the coded character.

By fixing the character group in the character storage unit, it is possible to decode the encoded character string from an arbitrary encoded character start position.

[Brief description of drawings]

FIG. 1 is a configuration diagram of a data compression device according to an embodiment of the present invention.

FIG. 2 is a flowchart showing a flow of an encoding process in the embodiment of the present invention.

FIG. 3A is a character storage unit 1 according to an embodiment of the present invention.
1 shows a character group inside 1 (B) shows an input character string 16 in the embodiment of the present invention (C) shows a list of codes output by the encoding unit 13 in the embodiment of the present invention D) is the character string matching determination unit 12 in the embodiment of the present invention.
Showing the output of

FIG. 4 is a flowchart showing a flow of a decoding process in the embodiment of the present invention.

FIG. 5 is a configuration diagram of a conventional information encoding / decoding device.

[Explanation of symbols]

 11 character storage unit 12 character string match determination unit 13 encoding unit 14 first decoding unit 15 second decoding unit 16 input character string 17 encoded character string 18 decoded character string

Claims (2)

[Claims] 1. A character storage unit for storing a character group, and a direction in which the input character string and the character group in the character storage unit are in coincidence with a start position in which the character group is coincident with a character length are determined. A character string matching determination unit, an encoding unit that encodes the position, length, and direction of the character group into an encoded character string, and the encoded character string is the position and length of the character group inside the character storage unit. And a second decoding unit for decoding the character group in the character storage unit from the position, length and direction of the character group into a decoded character string. Data compressor device. 2. The character string match determination unit outputs information indicating that the character in the input character string is not in the character group in the character storage unit, and the encoding unit information-encodes the state. The first code and the second code that encodes the characters that did not exist in the character storage unit are output, and the first decoding unit decodes the second code into the first code and the characters in the input character string. 2. The data compression device according to claim 1, wherein the second decoding unit decodes the character in the input character string immediately after the first code as a character in the decoded character string.