JPH05236283A - Compression decoding system for picture data - Google Patents

Abstract

PURPOSE:To improve the reliability of processing by judging whether data used for compression/decoding processing are regular data or erroneous data. CONSTITUTION:A picture data compression section 1 is provided with a pre- processing conversion section section 3, an intermediate data latch section 20, a universal coding section 4, a picture element number latch section 2, a counter section 21, and a comparing section 22. A decoding section 5 is provided with a universal decoding section 4A, an intermediate data latch section 20, a post processing conversion section 3A, a counter section 21, a comparing section 22 and a picture element number latch section 2. At picture data compression/ decoding, since the converted intermediate data are latched in the intermediate data latch section 20, a run length of intermediate data is counted by the counter section 21 and it is compared with a value in the picture element number latch section 2 at the comparing section 22 to detect whether or not erroneous data are in use.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a compression / decompression system for image data used in facsimile machines and various computer systems that handle black and white binary image data.

In recent years, OA (Office Automation)
Has been developed, and documents are handled as binary image information in a facsimile or an optical disk file system.

When the document information is used as digital data, the data amount of the image information is much larger than that of the character image and is ten to several tens times. Therefore, in order to handle image information efficiently in storage and transmission, it is essential to add efficient data compression and reduce the data amount.

[0004]

2. Description of the Related Art FIGS. 6 to 14 are views showing a conventional example, FIG. 6 is an explanatory view of a universal type (A is a universal type algorithm explanatory diagram, B is a universal type code format explanatory diagram), FIG. 7 is a flowchart of LZW encoding processing, FIG. 8 is a flowchart of LZW decoding processing, and FIG. 9A.
Is a specific explanatory diagram of LZW encoding, FIG. 9B is an explanatory diagram of a dictionary configuration example, and FIG. 10 is a specific explanatory diagram of LZW decoding.

FIG. 11 is a block diagram of the compression section and the decompression section (A is a block diagram of the compression section, B is a block diagram of the decompression section), and FIG.
13 is a configuration diagram of the compression unit, FIG. 13 is an explanatory diagram of intermediate data (A is an intermediate data format, B is data in a shift register, C is intermediate data), and FIG. 14 is a configuration diagram of the decompression unit.

In FIG. 11, 1 is a compression unit, 2 is a pixel number holding unit, 3 is a preprocessing conversion unit, 4 is a universal encoding unit, 3
A is a post-processing conversion unit, 4A is a universal decoding unit, and 5 is a restoration unit.

In FIG. 12, 6 is a buffer, 7 is an output selector circuit, 8 is a counter, 9 is a negative circuit (inverter), 10-1 to 10-4 are shift registers, and 11-1.
11-4 are registers, 12-1-12-4 are EOR
(Exclusive OR circuit), 13 indicates OR (OR circuit).

Further, in FIG. 14, 14 is an output control unit, 15 is a FIFO register, 16 is a counter, and 17 is a counter.
Is a register, 18-1 to 18-4 are shift registers, 1
9 indicates a register.

Conventionally, a universal encoding method has been known as a data compression method. This universal encoding method is an information storage type data compression method, and when data is compressed, the statistical properties of the information source are not assumed in advance.
It can be applied to various types of data (character code, object code, image, etc.).

Here, the universal code will be briefly described. A typical universal code is
There is a ZiV-Lempel code.
(For details, see, for example, Munakata “ZiV-Lempel Data Compression Method”, Information Processing, VoL, 26, No 1, 19
See 1985).

In the ZiV-Lempel code, the universal type and the incremental decomposition type (Incremental p
two algorithms have been proposed. The above two algorithms and their improved algorithms will be briefly described below.

(1) Universal type algorithm Although this algorithm has a large amount of calculation, a high compression rate can be obtained. This is a method in which encoded data is separated from an arbitrary position of a past data series into a series of the same maximum length (subsequence) and is encoded as a copy of the past series. A description will be given below with reference to the drawings.

FIG. 6 shows a universal type ZiV-Lemp.
The basic structure of an encoding unit for an el (Jib-Lempel) code is shown. In the encoding process of the encoding unit, the encoded data is divided into a sequence of the maximum length that matches from any position of the past data sequence, and encoded as a copy of the past sequence.

More specifically, as shown in FIG. 6A, a P buffer for storing coded input data and a Q buffer for storing data to be coded are provided.
The data series of the buffer is collated with all the partial series of the data series of the P buffer, and the partial series of the maximum length that matches in the P buffer is obtained.

Then, in order to specify this maximum length subsequence in the P buffer, "start position of the maximum length subsequence", "matching length (for example, number of words)",
A set (a set of information shown in B of FIG. 6) with “a symbol that causes a mismatch (for example, data of the next word)” is encoded.

Next, the encoded data sequence in the Q buffer is transferred to the P buffer, and a new data sequence for the encoded data sequence is input in the Q buffer. Hereinafter, by repeating the same processing, the data is decomposed into the partial series and the coding is executed.

As an improved type of the universal type algorithm, there is an LZSS code (for example, TC Be.
ll, "Better OPM / L Text Com
"pression", IEEE Trans, On C
ommun, VoL, COM-34, No. 12, De
c, 1986).

In the LZSS code, the start position of the maximum matching sequence in the P buffer, a set of matching lengths, and the next symbol are distinguished by a flag, and the one with the smaller code amount is coded.

(2) Incremental decomposition type algorithm The ZiV-Lempel (dib-Lempel) code incremental decomposition type algorithm is for incrementally decomposing and coding a series of input data, and has a universal compression rate. It is known to be worse, but simpler and easier to calculate.

In the incremental decomposition type ZiV-Lempel coding system, a sequence of input symbols is represented by X = aababab.
If aa ..., Component series x = X0X1X2 ...
The incremental decomposition into is as follows.

Let Xj be the longest sequence from which the rightmost symbols of the existing components have been removed, and X = a.ab.aba.b.aa.
・ ・ It becomes. Therefore, X0 = λ (empty column), X1 = X0
a, X2 = X1b, X3 = X2a, X4 = X0b, X5
= X1a, ...

For each component series that has been decomposed incrementally, the "component index" and the "next symbol" are used by using the existing component series.
Encoding with a set of. In other words, the incremental decomposition type algorithm finds a coding pattern that has the maximum length match among the previously decomposed partial sequences and encodes it as a copy of the previously decomposed partial sequences.

An LZW code is an improved version of the incremental decomposition type algorithm. (For example, T.
A. Welch, “A Technique for
High-Performance Data Com
compression ”, Computer, June 1
984).

The encoding / decoding process using the LZW code will be described below. First, the LZW encoding process has a rewritable dictionary, divides the input character string into different character strings (substrings), adds the reference numbers in the order in which they appear, and registers them in the dictionary. The character string currently input is represented by the reference number of the longest matching character string registered in the dictionary and is encoded.

FIG. 9A shows an explanatory diagram of LZW encoding, FIG. 10 shows an explanatory diagram of LZW decoding, and FIG. 9B shows an example of a dictionary structure created at the time of encoding and decoding.
It should be noted that in FIGS.
An example of compressing and decompressing data consisting of a combination of three characters c is taken up.

In the LZW encoding process of FIG. 7, first, in step S1, a character string consisting of one character for all characters is registered in the dictionary in advance as an initial value, and then encoding is started. In the encoding in step S1, the dictionary is searched by the input first character K to obtain the reference number ω, which is used as the initial character string.

Next, in step S2, the next character K of the input data is read, and in step S3, it is checked whether or not the character input is completed. Then, the process proceeds to step S4 and the initial character string ω obtained in step S1 It is searched whether or not the extended character string (ωK) to which the character K read in S2 is added is in the dictionary.

If the character string (ωK) is not found in the dictionary in step S4, the process proceeds to step S6, the reference number ω of the character K obtained in step S1 is output as the code word code (ω), and the character string (ωK) is also output. , A new reference number is added and registered in the dictionary, the input character K in step S2 is replaced with the reference number ω, the dictionary address n is incremented, and the process returns to step S2 to read the next character K.

On the other hand, if the character string (ωK) is found in the dictionary at step S4, the character string (ωK) is referred to as reference number ω at step S5.
, And returns to step S2 again, and in step S4, the search for the maximum matching length is continued until the character string (ωK) cannot be searched from the dictionary.

The LZW encoding will be specifically described with reference to FIG. 9 as follows. First, the input data in in FIG. 9A
Put is read from left to right. When you enter the first letter a, there is no matching string in addition to the letter a in the dictionary, so
The OUTPUT CODE 1 (reference number ω) is coded and output. Then, let the character a be the initial character string ω.

Next, if the second character b is input,
Extended character string ωK = which adds this input character to the initial character string ω
Since ab is not in the dictionary, OUTPUT C of the character b
Output ODE2 as a code word. Then, the extended character book ωK = ab is registered with the reference number 4 in the dictionary. The actual dictionary registration is registered as the character string 1b as shown on the right side of FIG. 9B. Then, the character b becomes the initial character string ω.

Next, if the third character a is input, an expanded character string ωK = b obtained by adding the initial character string ω to the character b.
Since a = 2a is not in the dictionary, the OUTPUT of the character a
After outputting CODE1 as a code word, the extended character string ω
K = ba is represented by 2a, and the reference number 5 is added to register it in the dictionary. Then, the character a becomes a new initial character string ω.

For the fourth input character b, the extended character string ωK = ab is already registered in the dictionary as the code word 4 of 1b, so the character string ωK is set as a new initial character string ω.
The second character c is input and the extended character string ωK = 4c = abc
make. Since this extended character string ωK = abc is not registered in the dictionary, OUTPUTC of the character string ab = 1b
ODE4 is output as a code word, and the extended character string ωK = ab
c is registered in the dictionary as codeword 6 in the form of 4c. This process is continued in the same manner thereafter.

The decoding process of FIG. 8 is the reverse operation of the encoding of FIG. In the LZW decoding of FIG. 8, as in the case of encoding, a character string consisting of one character for every character is registered as a first value in the dictionary in advance, and then decoding is started.

First, in step S1, the first code (reference number) is read and the current CODE is set to OLDcode,
Since the first code corresponds to any one-character reference number already registered in the dictionary, the character code (K) matching the input code CODE is searched for and the character K is output.

The output character K is set in FINchar for later exception processing. Next, in step S2, the next code is read and set in CODE as INcode. In step S3, it is checked whether or not there is a new code, that is, whether or not the code input is completed, and the process proceeds to step S4. It is checked whether or not the code CODE input in step S3 is defined (registered) in the dictionary. ..

Since the input code word is normally registered in the dictionary by the processing up to the previous time, the process proceeds to step S5, the character string code (ωK) corresponding to the code CODE is read from the dictionary, and the character K is read in step S6. Temporarily stack,
The reference number CODE (ω) is set as a new code CODE, and the process returns to step S5 again, and steps S5 and S6
The above procedure is recursively repeated until the reference number ω reaches one character K, and finally the process proceeds to step S7, where the characters stacked in step S6 are LIFO (Last In Fast).
(Out) pops up and outputs.

At the same time, in step S7, the code ω used last time and the first character K of the character string restored this time are combined (ω
A new reference number is added to the character string expressed as (K) and registered in the dictionary.

The LZW decoding process will be described in detail with reference to FIG. First, in FIG. 10, the first input codeword (INPUT CODE) is 1, and the letters a, b, and c are already registered in the dictionary as reference numbers 1, 2, and 3 as shown in FIG. Is output by replacing with the character string a of the reference number that matches the code word 1.

Similarly for the next code word 2, the character b
Replace with and output. Code word 1 processed last time
A new reference number 4 is added to the character string ωK = 1b, which is a combination of the first character b of the character string decoded this time, and registered in the dictionary.

The third code word 4 replaces the character string 1b obtained by the dictionary search with the character string ab and outputs the character string ab. At the same time, a character string ωK = 2a obtained by combining the previously processed code word 2 and the first character a of the character string decoded this time
A new reference number 5 is added to (= ba) and registered in the dictionary.

Similarly, this process is repeated. The above universal encoding method is an information storage type data compression method, and does not assume the statistical property of the information source at the time of data compression. Therefore, it can be applied to various types of data (character code, object code, image, etc.).

However, using the universal code, 2
When the value image data is compressed, a certain degree of compression ratio can be obtained, but the compression ratio of the conventionally used compression method for binary images (MMR, predictive coding) cannot be exceeded.

Therefore, conventionally, a method has been considered in which binary image data is converted into intermediate data represented by a set of a pixel pattern and a run length of the pattern, and the intermediate data is universally encoded. The outline will be described below.

FIG. 11 shows the configuration of the compression unit and the decompression unit of the image data according to the universal coding method. As shown in FIG. 11, the compression unit 1 is provided with a pixel number holding unit 2, a preprocessing conversion unit 3, and a universal encoding unit 4. The number-of-pixels holding unit 2 holds the number of horizontal pixels and the number of vertical pixels from the outside, and the preprocessing conversion unit 3 preprocesses the input image data to create intermediate data, and then the universal code. Encoding unit 4 performs encoding and outputs encoded data.

Further, the restoration unit 5 is provided with a pixel number holding unit 2, a universal decoding unit 4A and a post-processing conversion unit 3A.
In this restoration unit 5, the number of horizontal pixels and the number of vertical pixels from the outside are held in the pixel number holding unit 2, and the input coded data is decoded by the universal decoding unit 4A and converted into intermediate data. After that, the post-processing conversion unit 3A performs post-processing to restore the image data.

The details will be described below with reference to FIGS. First, the compression unit shown in FIG. 12 will be described. In FIG. 12, 11-i (i = 1 to 4) is a register of the i-th line, which holds black-and-white information of pixels at the same pixel position of the i-th line among the four adjacent lines read from the image data. 10-i (i = 1 to 4) is a shift register of the i-th line, which holds black-and-white information of all pixels of the i-th line in the four adjacent lines read from the image data, 12- i (i = 1 to 4) is an EOR circuit (exclusive OR circuit) of the i-th line, which is used for the black-and-white information of the pixel held by the i-th line register 11-i and the i-th line shift register 10-i. When both the black and white information of the pixel at the head position is black or white, "0" is output.

Further, 13 is an OR circuit (OR circuit), and four EOR circuits 12- of the i-th line are provided.
When "1" is output from any one of i,
A device that outputs “1”, and 9 is a negation circuit (inverter), which inverts the output of the first OR circuit 13
When all of the i-th line EOR circuits 12-i provided individually output "0", "1" is output to the counting terminal of the counter 8.

A part of the output selector circuit 7 is shown in FIG.
The shift register 10-corresponds to the pixel number holding unit 2 of 1A.
1-10-4, registers 11-1-11-4, EOR1
The 2-1 to 12-4, the OR circuit 13, the NOT circuit 9, the counter 8, the output selector circuit, and the like correspond to the preprocessing conversion unit 3.

The operation of the compression section will be described below with reference to FIGS.
This will be described with reference to FIG. When the binary image data is input to the shift register 10-4, the shift register 10-1
The data is stored in each of 10 to 4 while shifting by one line. First, the first pixels are read from the shift registers 10-1 to 10-4 and set in the registers 11-1 to 11-4, respectively.

After that, the shift registers 10-1 to 10-
The first pixel of No. 4 is read out, and the black-and-white of the read-out pixel is compared with the previous four-line black-and-white pattern in the registers 11-1 to 11-4, respectively. The comparison is performed by taking exclusive OR in the exclusive OR circuits 12-1 to 12-4. If the read black-and-white pattern for each line matches the previous black-and-white pattern for each line, 0 is output for each corresponding exclusive OR, and if not, 1 is output. These outputs are applied to the OR circuit 13.

(1) If the 4-line black-and-white pattern matches the previous 4-line black-and-white pattern, the logical sum 13
0 is output from. This output is inverted by the negation circuit 9 and then added to the counter 8 to set the counter 8 to 1
Count up one. When the count value reaches 15 in the counter 8, a carry is output, and this signal passes through the output selector circuit 7 and instructs the universal encoding unit 4 to perform encoding.

(2) If the 4-line black-and-white pattern does not match the previous 4-line black-and-white pattern, at least one of the exclusive OR circuits 12-1 to 12-4 has an output of 1. Therefore, 1 is output from the OR circuit 13.
This output signal passes through the output selector circuit 7 and instructs the universal encoding unit 4 to perform encoding.

The universal encoding unit 4 includes a pre-processing circuit, for example, as shown in FIG. 13C according to the format of FIG. 13A.
The intermediate data shown in is added, and the sequence of this intermediate data is encoded. The intermediate data in FIG. 13C consists of 8 bits, and the upper 4 bits are a collection (pixel pattern) of the contents of the registers 10-1 to 10-4, and the lower 4 bits are set with the counter value (run length). To be done.

Therefore, as shown in FIG. 13B, "1101"
If 4 pixels in the vertical direction of 10 are aligned in the horizontal direction,
Since the run length is "1001", intermediate data (4 bit pixel pattern + 4 bit run length)
Becomes "11011001" like 13C.

Next, after the intermediate data for one word is input to the universal encoding unit 4, the output of the output selector circuit 7 instructs the counter 8 to be cleared to -1 and the registers 11-1 to 11-11. -4 is instructed to newly set the read black and white pattern for four lines. Hereinafter, the same operation is repeated until each pixel is read from the registers 10-1 to 10-4 and all the pixels in the registers 10-1 to 10-4 are encoded. When the coding of all the pixels of the 4 lines is completed, the next 4 lines are registered in the register 10-
1 to 10-4, and the same operation is repeated until the entire image is encoded.

Next, regarding the image data restoration section,
This will be described with reference to FIG. In FIG. 14, a universal decoding unit 4A decodes the input coded data and converts it into intermediate data (8 bits in this example). A register 19 stores the intermediate data and stores a pixel pattern of 4 bits. It is a register for dividing into 4 bits of bit and run length.

The counter 16 counts run lengths, and the shift registers 18-1 to 18-4 shift the data according to the output of the register 17 and the count value of the counter to create duplicated data. , FIFO
Reference numeral 15 is an output register.

The output control section 14 inputs the run length from the register 19 and the numbers of horizontal pixels and vertical pixels from the outside to control the shift register. Less than,
The processing of the restoration unit 5 will be briefly described.

The coded data from the outside is decoded by the universal decoding unit 4A and becomes intermediate data (8
bit). This intermediate data is temporarily stored in the register 19, and the pixel pattern (4 bits) and the run length (4
Bit) and are divided into.

The divided image data is stored in the register 1
7, and the run length is input to the counter 16 and the output control unit 14. After that, the pixel pattern of the register 17 is input to the shift registers 18-1 to 18-4, where it is shifted by the count value of the run length output from the counter 16.

That is, the same pattern is duplicated by the run length value to restore the original image data. Then, according to an instruction from the output control unit 14, the shift registers 18-1 to 18-1
The data 8-4 is output, and the restored image data is output via the register 15 of the FIFO.

[0063]

SUMMARY OF THE INVENTION The above-mentioned conventional device has the following problems. (1) The conventional image data compression / decompression method (see FIGS. 11 to 14) was conceived on the premise that no hardware error occurs during processing.

Therefore, for example, if an error occurs in the communication path, it will affect the code data and prevent normal processing. (2) In universal encoding, a dictionary is created in an area secured on a storage device and processing is performed using the dictionary.

In this case, it is established under the precondition that the data in the storage device will not be destroyed by an external factor or the like. However, when it is configured as an image data compression / decompression device, there are problems such as damage to the storage device and garbled data.

At this time, even if erroneous data was read out and used for processing, it was not possible to determine whether it was legitimate data or erroneous data. The present invention solves such a conventional problem and makes it possible to determine in the middle of processing whether the data used in the compression / decompression processing of image data is legitimate data or erroneous data. The purpose is to improve the reliability of processing.

[0067]

FIG. 1 is a diagram for explaining the principle of the present invention, in which the structure of the compression unit of A in FIG. 1 and the structure of the decompression unit in FIG. 1 are shown.

In the figure, 1 to 5 are the same as those in FIG. Further, 20 is an intermediate data holding unit, 21 is a counting unit, 2
2 shows a comparison part. The present invention has the following configuration to solve the above problems.

(1) In the image data compression method for compressing image data composed of pixels in a two-dimensional array, the image data is converted into intermediate data expressed as a set of a pixel pattern and a run length of the pattern. A preprocessing conversion unit 3, a pixel number holding unit 2 that holds the number of horizontal / vertical pixels of the image data to be encoded, and a counting unit 21 that counts the run length of the intermediate data converted by the preprocessing conversion unit 3. And a comparison unit 22 that compares the value counted by the counting unit 21 with the value held by the pixel number holding unit 2, and a universal code that universally encodes the intermediate data converted by the preprocessing conversion unit 3. And an encoding unit 4 for converting input image data into intermediate data, universally encoding the intermediate data to output encoded data, and performing the comparison in the process of the process. Based on the comparison result of the section 22, it is detected that wrong data is used.

(2) The universal coding of the above configuration (1) is called universal type universal coding. (3) The universal coding of the above configuration (1) is called incremental decomposition type universal coding.

(4) Image data for restoring image data from universally encoded data of intermediate data represented by a set of a pixel pattern of image data composed of pixels in a two-dimensional array and its pattern run length In the data restoration method, a universal decoding unit 4A that universally decodes the coded data and converts it into intermediate data, and a pixel number holding unit 2 that holds the number of horizontal / vertical pixels of the image data to be decoded. , The universal decoding unit 4A
A counting unit 21 for counting the run length of the intermediate data converted in step 1, a comparing unit 22 for comparing the value counted by the counting unit 21 with a value held by the pixel number holding unit 2, and the universal decoding From the intermediate data converted in part 4A,
A post-processing conversion unit 3A for outputting a pixel pattern corresponding to the run length of the intermediate data and converting the pixel data into image data, converting the input encoded data into intermediate data,
While restoring the intermediate data to image data and outputting the image data,
In the process of the processing, it is detected based on the comparison result of the comparison unit 22 that wrong data is used.

(5) The universal encoding of the above configuration (4) is called universal type universal encoding. (6) The universal encoding of the above configuration (4) is set to incremental decomposition type universal encoding.

[0073]

The operation of the present invention based on the above construction will be described with reference to FIG. (Compressor) ... See A of FIG. 1. In advance, the number of horizontal pixels and the number of vertical pixels provided from the outside are held in the pixel number holding unit 2. In this state, when the image data is input to the preprocessing conversion unit 3, preprocessing is performed to convert the data into intermediate data (pixel pattern + pattern run length), and the intermediate data holding unit 20 holds the intermediate data.

The run length (pattern run length) of the intermediate data is counted by the counter 21, and the count value is sent to the comparator 22. In the comparison unit 22, the count value is
The value stored in the pixel number storage unit 2 is compared, and error information is output according to the result.

The intermediate data held in the intermediate data holding unit 20 is sent to the universal coding unit 4, where it is universally coded and converted into coded data, that is, compressed data and output. To do.

In this way, when erroneous data is read and used for processing due to a hardware failure of the communication device or the storage device, it is detected during the processing (error information). ..

(Restoring Unit) ... See B in FIG. 1 In this case as well, the pixel number holding unit 2 holds the number of horizontal pixels and the number of vertical pixels. When the encoded data is input to the universal decoding unit 4A, it is universally decoded here and converted into intermediate data.

The intermediate data is stored in the intermediate data holding unit 20.
The run length is counted by the counter 21, and the count value is sent to the comparator 22. Comparison unit 22
Then, the count value is compared with the value held in the pixel number holding unit 2, and error information is output according to the result.

Further, the intermediate data held in the intermediate data holding unit 20 is sent to the post-processing conversion unit 3A, where it is restored to the original image data. In this way, similar to the compression unit, when erroneous data is read and used for processing, it is detected during processing. Therefore, the reliability of the image data compression / decompression process can be improved.

[0080]

Embodiments of the present invention will be described below with reference to the drawings. 2 to 5 are diagrams showing an embodiment of the present invention, FIG. 2 is a process explanatory diagram (during compression), FIG. 3 is a process explanatory diagram (during restoration), FIG. FIG. 5 is a block diagram of the restoration unit.

In the figure, the symbols 1 to 5 in FIG. 1, FIG. 12 and FIG. 14 are the same. In addition, 23 is a pixel adder, 2
Reference numerals 4 and 27 denote comparators, 25 and 26 denote registers, and 28 denotes a line adder.

(1) Description of Outline of Image Data Compression / Decompression Process First, the outline of the process of this embodiment will be described with reference to FIGS. (Image data compression processing) ... See FIG. 2. In this embodiment, the image data to be processed is binary black and white image data.

For example, as shown in FIG. 2, the original image (original image data) will be described as having 55 bits horizontally and 4 bits vertically. Preprocessing is performed from this original image to create intermediate data.

In this case, the format of the intermediate data is
Pixel pattern 4 bits + count number (run length) 4
The total bit structure is 8 bits. In this format, run lengths are counted in a range of up to 16.

For the intermediate data, vertical 4 bits are cut out from an original image of (vertical 4 bits) × (horizontal 55 bits), and the pixel pattern and the run length of the pattern are combined to form 8-bit intermediate data. To do.

For example, assuming that black is "1" and white is "0" in the figure, the vertical 4 bits are "1000" and "0" from the left side of the original image.
"001", "0011", "0011", "011"
1 ”,“ 0111 ”,“ 1110 ”,“ 1100 ”,
"1100", "1000", "1000", "100"
0 ”...

Therefore, from the left side of the figure, the run length of "1000" is 1, the run length of "0001" is 1, and the run length is "0".
"011" has a run length of 2, "0111 has a run length of 2," 1110 "has a run length of 1," 110 "
The run length of "0" is 2, the run length of "1000" is 3, and so on.

Therefore, if there is only one identical image pattern and the run length is added to this pixel pattern to form intermediate data, the following intermediate data is obtained from the left side of the drawing.

When the run length of the pixel pattern is represented by 4 bits, the run length 1 is "0000", the run length 2 is "0001", and the run length 3 is "001".
0 ”, the run length 4 is“ 0011 ”, and the run length 16 is“ 1111 ”. As a result, 16-bit run length can be represented by 4 bits.

That is, from the left side of the figure, "1000000
0 "," 00010000 "," 00110001 ",
"01110001", "11100000", "11"
Intermediate data such as "000001", "10000010" ... Is obtained.

In the intermediate data, by adding the run length, the image data of the same pattern is omitted, and the amount of data is smaller than that of the original image by that amount. Therefore,
Since the amount of data is reduced by the preprocessing before the encoding process, the compression process can be speeded up accordingly.

Next, the run length of the intermediate data is counted to check that incorrect data has been used, and universally encoded to obtain encoded data. After that, the data of (vertical 4 bits) × (horizontal 55 bits) (4 lines of data) in the figure is used as one unit for sequential encoding processing and image data compression processing.

It should be noted that the run lengths for the first and fourth lines are summed to 55. This count value is compared with the number of pixels of the original image given from the outside, and in the encoding process,
Check if incorrect data was used.

(Image Data Restoration Processing) ... See FIG. 3. The encoded data once compressed by the universal encoding processing is decoded by universal decoding and converted into intermediate data.

After that, the intermediate data becomes a restored image by post-processing. Also in this case, the intermediate data is composed of a 4-bit pixel pattern and a 4-bit run length. Further, it is checked whether or not incorrect data is used by using the run length count value.

(2) Detailed Description of Compressing Unit (Structure of Compressing Unit) ... See FIG. 4 In the present embodiment, when compressing image data, the compressing unit having the structure shown in FIG. 4 is used.

The compression unit 1 includes a shift register 10-1.
-10-4, registers 11-1 to 11-4, EOR (exclusive OR circuit) 12-1 to 12-4, OR (OR circuit) 13, NOT circuit (inverter) 9, counter 8, output selector Circuit 7, buffer 6, universal encoding unit 4, pixel adder (pixel adder) 23, line adder (line adder) 28, comparators 24, 27, register 25,
It is composed of 26 etc.

In the above structure, the shift register 10-
1-10-4, registers 11-1-11-4, EOR1
2-1 to 12-4, OR 13, NOT circuit 9, counter 8, and output selector circuit 7 correspond to the preprocessing conversion unit 3 of FIG. 1, and the buffer 6 corresponds to the intermediate data holding unit 20.

Further, the pixel adder 23 and the line adder 28
Corresponds to the counting unit 21 in FIG. 1, and the comparators 24 and 27 are
This corresponds to the comparison unit 22 in FIG. Further, a part of the output selector circuit 7 and the registers 25 and 26 correspond to the pixel number holding unit 2 of FIG.

The pixel adder 23 and the line adder 2
The configuration other than 8, the comparators 24 and 27, and the registers 25 and 26 is the same as that of the conventional example. Shift register 10-1
Numerals 10 to 4 are for sequentially storing the input image data while shifting them, and for storing the original image for 4 lines of 4 bits × 55 bits shown in FIG.

In this case, the shift register 10-1 has
55-bit image data on the first line, 55-bit image data on the second line in the shift register 10-2, 55-bit image data on the third line in the shift register 10-3, shift register 10-4 Is 5 on the 4th line
5-bit image data is stored therein.

The registers 11-1 to 11-4 store the data of one pixel (1 bit) output from the shift registers 10-1 to 10-4, and are arranged in the vertical direction of FIG.
Bit image data is sequentially stored.

EOR 12-1 to 12-4 are register 1
Data stored in 1-1 to 11-4 (1 bit)
And a next data (1 bit) stored in the shift registers 10-1 to 10-4 (exclusive OR operation) (a circuit for performing a run length calculation).

The counter 8 has EORs 12-1 to 12-4.
The output data of is counted and the run length is counted. In this example, the run length of the intermediate data is 4
Because of the bit configuration, 4 bits are taken out from the LSB of the counter 8 and set in the buffer 6.

In the 4-bit run length, "0
Since it is in the range of 000 "to" 1111 "(maximum 16), a carry signal when the count value of the counter 8 exceeds 15 is taken out and input to the output selector circuit 7.

In the output selector circuit 7, the number of horizontal pixels (55 in this example) and the number of vertical pixels (4 in this example) given from the outside are set inside and the register 11-
1 to 11-4 data (4-bit vertical data),
Input the output data of OR13, etc., register 11-1 ~
11-4 and the counter 8 are controlled.

The buffer 6 temporarily stores the intermediate data (4-bit pixel pattern + 4-bit run length), and the universal encoder 4 universally encodes the intermediate data to encode the intermediate data. It is to be converted into digitized data.

The pixel adder 23 is an adder that inputs the run length added to the lower 4 bits of the intermediate data stored in the buffer 6 and adds the pixels.
The line adder 28 is a pixel adder carry.
It is an adder that adds signals and adds the number of lines (in units of 4 lines).

The register 25 is a register for storing the number of horizontal pixels (55 in this example) given from the outside, and the register 26 has a value (1/4) of the total number of vertical pixels given from the outside ( This is a register for storing 1/4 because it is processed in units of 4 lines.

The comparator 24 is a comparator for comparing the added value of the pixel adder 23 and the value of the register 25, and the comparator 27
Is a comparator for comparing the added value of the line adder 28 and the value of the register 26.

(Operation of Compressing Unit) ... See FIGS. 2 and 4. When binary image data is input to the shift register 10-4, 1 is input to each of the shift registers 10-1 to 10-4.
It is stored while shifting line by line. First, the first pixels are read from the shift registers 10-1 to 10-4 and set in the registers 11-1 to 11-4, respectively.

After that, the shift registers 10-1 to 10-
The first pixel of No. 4 is read out, and the black-and-white of the read-out pixel is compared with the previous four-line black-and-white pattern in the registers 11-1 to 11-4, respectively. The comparison is performed by taking an exclusive OR with EOR (exclusive OR circuit) 12-1 to 12-4.

If the read black-and-white pattern for each line matches the previous black-and-white pattern for each line, 0 is output for each corresponding exclusive OR, and if they do not match, 1 is output. .. These outputs are OR (OR circuit)
Added to 13.

(1) If the 4-line black-and-white pattern matches the previous 4-line black-and-white pattern, the logical sum 13
0 is output from. This output is inverted by the NOT circuit 9 and then added to the counter 8 to set the counter 8 to 1
Count up one. The counter 8 outputs a carry when the count value reaches 15, and this signal instructs the universal encoder 4 via the output selector circuit 7 to perform encoding.

(2) If the black-and-white pattern of four lines does not match the previous black-and-white pattern of four lines, at least one of the exclusive OR circuits 12-1 to 12-4 has an output of 1. Therefore, 1 is output from the OR circuit 13.
This output signal passes through the output selector circuit 7 and instructs the universal encoding unit 4 to perform encoding.

The universal encoding unit 4 receives the intermediate data created by the preprocessing circuit, where it is subjected to universal encoding processing and converted into encoded data. Next, after the intermediate data for one word is input to the universal encoding unit 4, the output of the output selector circuit 7 is the counter 8
To clear to -1 and register 1
It instructs 1-1 to 11-4 to newly set the read black and white patterns for four lines.

Below, from registers 10-1 to 10-4 to 1
The pixels are read out pixel by pixel, and the same operation is repeated until all the pixels in the registers 10-1 to 10-4 are encoded. When the coding of all the pixels of four lines is completed, the next four lines are input to the registers 10-1 to 10-4 and the same operation is repeated until the entire image is coded.

The encoding process is executed as described above. In the process, it is judged whether the data being processed is regular data or erroneous data. Hereinafter, this process will be described.

First, before starting the processing, the register 25
, The number of lateral pixels given from the outside (55 in the example of FIG. 2)
Is stored in the register 26, and 1/4 of the total vertical pixel number
(In the example of FIG. 2, since it is processed in units of 4 lines, it is set to 1/4).

When the processing is started, the intermediate data (4-bit pixel pattern + 4-bit run length) converted in the pre-processing is stored in the buffer 6. Therefore, the run length (lower 4 bits) of the intermediate data is extracted,
The pixel adder 23 adds. This added value is calculated by the comparator 24.
Is compared with the value (55) of the register 25.

In this comparison, the added value of the pixel adder 23 is
If it is smaller than the value of the register 25, the run lengths are continuously added. 2 (vertical 4 bits) x (horizontal 5) shown in FIG.
When the processing of 4 lines (5 bits) is completed, the value of the pixel adder 23 becomes equal to the value of the register 25 (becomes 55) if there is no error.

In this way, when the value of the pixel adder 23 and the value of the register 25 become equal, the pixel adder 23 is cleared (clr) and the carry signal (cry) is input to the line adder 28 (the line adder is incremented by 1). ).

Then, in the pixel adder 23, the next 4
The addition is started for the line portion and the above operation is repeated. Further, when an error occurs in the data and the processing for four lines is completed, the value of the pixel adder 23 and the register 25
The values of may not be equal.

In such a case, in the comparator 24, if the value of the pixel adder 23 is larger than the value of the register 25,
An error signal is output, but if the value of the pixel adder 23 is smaller than the value of the register 25, nothing is done.

However, when the value of the pixel adder 23 is smaller than the value of the register 25, the pixel adder 23 is not cleared even after the processing for four lines is completed. Therefore, even if the processing for the next four lines is started, the addition is continued to the added value for the previous four lines. Therefore, during processing of the next four lines, the value of the pixel adder 23 becomes larger than the value of the register 25, and an error signal is output.

As described above, the processing is performed in units of four lines, and the line adder 28 continues the addition. In the comparator 27, the value of the line adder 28 is compared with the value of the register 26, and when the processing for the total number of vertical pixels is normally completed, both values become equal, so nothing is output, but both are If they are not equal, an error signal is output.

As described above, by detecting the error signal, it is possible to know whether the coding process is performed with the regular data or the erroneous data. (3) Detailed description of decompression unit (configuration of decompression unit) ... See FIG. 5. The encoded data encoded by the compression unit is decompressed by the decompression unit 5 shown in FIG. It becomes an image (original picture).

The restoring unit 5 is a universal decoding unit 4
A, registers 17, 19, counter 16, shift registers 18-1 to 18-4, FIFO register 15, output control unit 14, pixel adder 23, line adder 28, comparators 24, 27, registers 25, 26, etc. Composed.

The correspondence relationship between the above configuration and FIG. 1B is as follows. The register 19 corresponds to the intermediate data holding unit 20, and includes a register 17, a counter 16, an output control unit 14,
The shift registers 18-1 to 18-4 and the FIFO register 15 correspond to the post-processing conversion unit 3A.

In addition, the pixel adder 23 and the line adder 28
Corresponds to the counting unit 21, and the comparators 24 and 27 include the comparing unit 22.
The registers 25 and 26 and a part of the output control unit 14 correspond to the pixel number holding unit 2.

The universal decoding unit 4A, the register 19, the register 17, the counter 16, the output control unit 14, the shift registers 18-1 to 18-4, and the FIFO register 15 are the same as those in the conventional example, and the description thereof is omitted. To do.

Further, the pixel adder 23 and the line adder 2
8, the comparators 24 and 27, and the registers 25 and 26 are the same as those in FIG. (Operation of decompression unit) ... See FIGS. 3 and 5 Encoded data from outside (data compressed by compression unit)
Is decoded by the universal decoding unit 4A to become intermediate data (4-bit pixel pattern + 4-bit run length) and stored in the register 19.

After that, the intermediate data is divided into two and divided into four.
The bit pixel pattern is input to the register 17, and the 4-bit run length is stored in the counter 16, the output control unit 14,
Input to the pixel adder 23.

At this time, the output control unit 14 has already stored the number of horizontal pixels and the number of vertical pixels given from the outside. The register 25 stores the number of horizontal pixels, and the register 26 stores 1/4 of the total number of vertical pixels.

The image pattern input to the register 17 is
It is a vertical 4-bit pixel pattern of FIG. 3, and the patterns of the respective pixels are shift registers 18-1 to 18-18, respectively.
-4 (1 bit at a time).

Here, since the count value of the counter 16 is the run length, this run length is sent to the shift registers 18-1 to 18-4, and the pattern (1 or 0) of the input pixel is equal to the run length. Shift
Duplicate the pattern.

This processing is sequentially performed for each intermediate data,
Four lines of the original image are restored in the shift registers 18-1 to 18-4. Then, the output control unit 14 controls the output of the shift registers 18-1 to 18-4, and outputs the restored image data via the register 15 of the FIFO.

In the process of such a restoration process, it is checked whether the data is restored by the regular data or the incorrect data. This processing is performed by the pixel adder 23, the line adder 28, the comparators 24 and 27, and the registers 25 and 26, but since it is the same as the processing of the compression unit shown in FIG. 4, description thereof will be omitted.

Also in this case, by detecting the error signals output from the comparators 24 and 27, it is possible to know whether the restoration processing is performed with the normal data or the restoration processing with the incorrect data. Become.

[0140]

As described above, the present invention has the following effects. (1) During the compression / decompression process of image data by encoding / decoding, it is possible to determine whether the data being processed is legitimate data or erroneous data.

(2) From the result of (1) above, it is possible to determine the invalidity of the encoding / decoding operation during the processing. (3) The reliability of image data compression / decompression processing is improved.

[Brief description of drawings]

FIG. 1 is a principle diagram of the present invention.

FIG. 2 is an explanatory diagram of processing in the embodiment of the present invention (when compressed)
Is.

FIG. 3 is a diagram for explaining the processing of the embodiment (at the time of restoration).

FIG. 4 is a configuration diagram of a compression unit in the embodiment.

FIG. 5 is a configuration diagram of a restoration unit in the embodiment.

FIG. 6 is an explanatory diagram of a universal type, A is an explanatory diagram of a universal type algorithm, and B is an explanatory diagram of a universal type code format.

FIG. 7 is a flowchart of a conventional LZW encoding process.

FIG. 8 is a flowchart of a conventional LZW decoding process.

9A is a concrete explanatory diagram of conventional LZW encoding, and FIG. 9B is an explanatory diagram of a dictionary configuration example.

FIG. 10 is a specific explanatory diagram of conventional LZW decoding.

FIG. 11 is a configuration diagram of a conventional compression unit and decompression unit.

FIG. 12 is a configuration diagram of a conventional compression unit.

FIG. 13 is an explanatory diagram of intermediate data, where A is the format of the intermediate data, B is the data in the register and C is the intermediate data.

FIG. 14 is a configuration diagram of a conventional restoration unit.

[Description of Codes] 1 compression unit 2 pixel number holding unit 3 pre-processing conversion unit 4 universal coding unit 20 intermediate data holding unit 21 counting unit 22 comparison unit 3A post-processing conversion unit 4A universal decoding unit

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Shigeru Yoshida 1015 Kamiodanaka, Nakahara-ku, Kawasaki-shi, Kanagawa Fujitsu Limited

Claims (6)

[Claims] 1. A method of compressing image data for compressing image data composed of pixels in a two-dimensional array, wherein the image data is converted into intermediate data expressed as a set of a pixel pattern and a run length of the pattern. A pre-processing conversion unit (3), a pixel number holding unit (2) that holds the number of horizontal / vertical pixels of image data to be encoded, and a run length of the intermediate data converted by the pre-processing conversion unit (3). A counting unit (21) for counting, a comparing unit (22) for comparing the value counted by the counting unit (21) with a value held by the pixel number holding unit (2), and the preprocessing conversion unit A universal encoding unit (4) that universally encodes the intermediate data converted in (3), converts the input image data into intermediate data, universally encodes the intermediate data, and encodes the encoded data. output A compression method of image data, characterized in that, in the course of the processing, it is detected that erroneous data has been used based on the comparison result of the comparison unit (22). 2. The image data compression method according to claim 1, wherein the universal encoding is universal universal encoding. 3. The image data compression method according to claim 1, wherein the universal encoding is an incremental decomposition type universal encoding. 4. An image for reconstructing image data from universally encoded data, which is universal data of intermediate data represented by a set of a pixel pattern of image data composed of pixels in a two-dimensional array and a run length of the pattern. In the data restoration method, a universal decoding unit (4A) that universally decodes the coded data and converts it into intermediate data, and a pixel number holding unit that holds the number of horizontal / vertical pixels of the image data to be decoded (2), a counting unit (21) for counting the run length of the intermediate data converted by the universal decoding unit (4A), and a value counted by the counting unit (21) for the pixel number holding unit (2 ) Of the intermediate data converted by the universal decoding unit (4A) and the comparison unit (22) for comparing the value held in) with the run length of the intermediate data. A post-processing conversion unit (3A) for outputting a pixel pattern and converting it into image data, converting input coded data into intermediate data, restoring the intermediate data into image data, and outputting the image data. A method of restoring image data, characterized in that, in the process of the processing, it is detected that erroneous data is used based on the comparison result of the comparison unit (22). 5. The image data restoration method according to claim 4, wherein the universal decoding is universal type universal decoding. 6. The image data restoration method according to claim 4, wherein the universal decoding is an incremental decomposition type universal decoding.