JPH0823447A - Coding processing unit and coding decoding processing unit - Google Patents

Abstract

PURPOSE:To improve compression efficiency more in the case of data coding. CONSTITUTION:Received grey level image data are extracted sequentially for each image block by a CPU 12 and a quantity of a grey level change of each block is discriminated. A dither processor 20 converts respective blocks into dither image data. Then the CPU 12 uses a rearrangement processing section 22 to rearrange dots as to an image block whose grey level change is discriminated to be small and to replace data of the image block whose grey level change is discriminated to be large with data of any block whose data are rearranged and then expands the received block data in an image memory 28. The CPU 12 arranges lines of expanded image data in lateral and longitudinal directions into a prescribed sequence and the image data after the rearrangement are given to a coding section 24, in which the data are subjected to run length coding.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a coding processing apparatus and a coding / decoding processing apparatus, and in particular, a multi-valued image is binarized by dither processing, and a pseudo halftone image obtained by this is coded. And a coding / decoding processing device for coding / decoding the pseudo-halftone image.

[0002]

2. Description of the Related Art In recent years, in the fields of facsimile machines, copying machines, image filing systems, etc., digital processing of images has been performed relatively frequently. In such an image digital processing apparatus, the image density data is set to 2 for each dot (pixel) by using a threshold matrix (dither matrix).
A dither method for performing half-value processing and displaying a halftone (pseudo-halftone) image is relatively often used.

However, since an image obtained by such a dither method has little continuity due to scattered black pixels and white pixels, it is compressed and encoded by the MH (Modified Huffman) method or the MR (Modified Read) method. However, the compression effect was not obtained so much, and conversely the data amount increased.

In order to improve such a problem, after converting a grayscale image such as a photograph into a pseudo halftone image (dither processing), the dots of the dither image are rearranged so that the subsequent run length compression processing is performed. An encoding processing method and apparatus for improving the compression efficiency of the above is disclosed in Japanese Patent Laid-Open No. 62-284591.

That is, when the grayscale image data as shown in FIG. 13A is dithered using the dither matrix as shown in FIG. Pixels having density values are binarized such that black pixels and pixels smaller than the threshold are white pixels, and a dither image as shown in FIG. By rearranging the pixels of each image block forming this dither image in the order of the threshold size of the dither matrix, binary image data as shown in (D) of the figure is obtained.
However, in FIG. 6D, the rightmost block in the figure is not rearranged.

This is because, as a result of the dot rearrangement process being performed in an image block in which the density change in the block is gentle, black pixels are arranged in the upper part of the image block and white pixels are arranged in the lower part of the image block. This tends to increase the efficiency of the subsequent run length compression, but in the image block where the density change in the block is sharp, the black-and-white distribution is dispersed due to the rearrangement process. Is.

For this reason, the above-mentioned Japanese Patent Laid-Open No. 62-284591 is used.
In the technique disclosed in Japanese Patent Publication, a dot density difference is calculated for each block (dither matrix size) of the input grayscale image, and whether or not the dot rearrangement process of the dither image is executed depending on the magnitude of this value. By determining, the image block in which the density change in the block is sharp is extracted, and the rearrangement processing is not performed in this block, thereby further increasing the efficiency of the run length compression.

[0008]

However, according to the technique disclosed in the above-mentioned Japanese Patent Laid-Open No. 62-284591,
Since only the dot rearrangement process as described above is performed as the pre-process of the compression encoding process, it cannot be said that the compression efficiency in encoding is not always satisfactory. For these reasons, the advent of a coding / compressing device that can further improve the compression efficiency has been desired.

However, since the encoding and the decoding are two sides of the same coin, if the compression efficiency at the time of encoding is simply improved,
A device for improving the compression efficiency may cause deterioration of the image quality of a decoded image.

The present invention has been made under the above circumstances, and a first object thereof is to provide an encoding processing device capable of further improving the compression efficiency in data encoding. is there.

A second object of the present invention is a coding / decoding processing apparatus capable of further improving the compression efficiency at the time of data coding without inviting the image quality deterioration of the image obtained after decoding. To provide.

[0012]

According to the first aspect of the present invention,
An encoding processing device comprising an encoding means for compressing and encoding image data, comprising block extraction means for sequentially extracting image blocks of a predetermined size from the grayscale image data, and a change in grayscale of each of the extracted image blocks. A judging unit for judging the magnitude, a dither processing unit for dithering each image block extracted by the block extracting unit by using a predetermined dither matrix to convert the image block into dither image data, and a small change in shading by the judging unit. For the image block determined to be, the dither image data is converted to binary data in which each pixel data is rearranged in the order of the size of the threshold value which is an element of the dither matrix, and the determination unit is used to change the density. For the replacement image block determined to have a large change, the dither image data of the image block A replacement unit that replaces the binary data of any of the blocks that have been sorted by the sorting unit, first and second storage units for storing image data, and before replacement of the replacement image block. Storing the dither data of the image data in the first storage means and the binary data of the image blocks rearranged by the rearranging means and the binary data of the image blocks rearranged by the replacing means. Storage means for storing and expanding in the storage means, and line rearranging means for rearranging the horizontal lines or the horizontal and vertical lines of the image data expanded in the second storage means in a predetermined order. And the dither data before replacement of the replacement image block stored in the first storage means and the line rearrangement means The gills image data after was having a coding control means for transferring to said encoding means.

According to a second aspect of the present invention, there is provided a coding / decoding processing device comprising a coding means for compressing and coding image data and a decoding means for decoding the coded data. A first block extracting means for sequentially extracting image blocks of a predetermined size; a determining means for determining the magnitude of the grayscale change of each of the extracted image blocks and creating determination result identification data indicating a determination result; and the block The dither processing means for dithering each image block extracted by the extracting means using a predetermined dither matrix to convert it into dither image data, and the image block determined by the determining means to have a small grayscale change, Each pixel data of the dither image data of the image block is rearranged in the order of the size of the threshold which is an element of the dither matrix. And sorting means for converting the data,
For the replacement image block determined to have a large change in shading by the determination means, the dither image data of the image block is converted into binary data of any block which has been sorted by the sorting means. First replacing means for replacing and a first storing means for storing image data
And second storage means, the dither data before replacement of the replacement image block is stored in the first storage means, and the image block data rearranged by the rearranging means and the replacement processing by the replacing means. Storage control means for storing the expanded image block data in the second storage means and expanding the same, and horizontal lines or horizontal and vertical lines of the image data expanded in the second storage means. Line sorting means for sorting in a predetermined order, the determination result identification data, the dither data before replacement of the replacement image block, and the image data sorted by the line sorting means are transferred to the coding means. Encoding control means and the horizontal lines or the horizontal and vertical lines of the decoded image data in the original order. And arranged return line side by side-back means,
Second image block extraction means for sequentially extracting image blocks of the same size as the image blocks extracted by the first block extraction means from the image data after the rearrangement processing by the line rearrangement means, and the decoded image blocks. When the determination result identification data indicates that the density change of the input image block is small, the rearrangement means for rearranging each pixel of the image data of the image block extracted by the second image block extraction means to the original arrangement. And the decoded determination result identification data indicates that the density change of the input image block is large, the image data of the image block extracted by the second image block extraction means is replaced with the decoded replacement image. Second replacement means for replacing the block with the dither image data before replacement.

[0014]

According to the encoding processing apparatus of the first aspect, the block extracting means sequentially extracts image blocks of a predetermined size from the input grayscale image data (multivalued image data). The judging means judges the magnitude of the change in shading of each of the extracted image blocks. At the same time, the dither processing unit dither-processes each image block extracted by the block extracting unit using a predetermined dither matrix to convert the image block into dither image data.

Binary data obtained by rearranging each pixel data in the order of the size of the threshold value which is an element of the dither matrix for the image block which the rearrangement means has determined that the gradation change is small. Convert to. On the other hand, with respect to the replacement image block for which the determining unit has determined that the gradation change is large in the replacing unit, the dither image data of the image block is rearranged by the rearranging unit until 2 of any one of the blocks has been rearranged. Replace with value data. The processes of the rearrangement unit and the replacement unit are performed for each image block.

In the storage control means, the dither data before replacement of the replacement image block is stored in the first storage means, and the binary data of the image block rearranged by the rearrangement means and the image processed by the replacement means are replaced. The binary data of the block is stored in the second storage means and expanded.

Next, in the line rearranging means, the horizontal lines of the image data expanded in the second storage means are rearranged in a predetermined order, or both the horizontal and vertical lines are arranged in a predetermined order. Sort. This is because by rearranging the lines, pixels can be arranged so that the continuity of black pixels or white pixels is further improved.

The encoding control means transfers the dither data before replacement of the replacement image block stored in the first storage means and the image data rearranged by the line rearranging means to the encoding means. To do.

As a result, each data transferred by the encoding means is compression-encoded (run-length encoding).

Next, the operation of the encoding / decoding processing device according to the second aspect will be described separately for encoding and decoding. << Encoding >> The first block extracting means sequentially extracts image blocks of a predetermined size from the input grayscale image data. The determination means determines the magnitude of the change in grayscale of each of the extracted image blocks and creates determination result identification data indicating the determination result. At the same time, the dither processing unit dither-processes each image block extracted by the block extracting unit using a predetermined dither matrix to convert it into dither image data.

With respect to the image block for which the judgment unit judges that the gradation change is small, the dither image data of the image block is rearranged for each pixel data in the order of the threshold value which is an element of the dither matrix. Converted to binary data. On the other hand, with respect to the replacement image block that the first replacement means has determined that the shade change is large by the determination means, the dither image data of that image block has been rearranged by the rearrangement means. Replace with the binary data of the block. Each processing of these rearrangement means and replacement means,
This is performed for each image block.

In the storage control means, the dither data before replacement of the replacement image block is stored in the first storage means and the data of the image block rearranged by the rearranging means and the image block rearranged by the replacing means are stored. The data and the data are stored in the second storage means and expanded.

Next, the line rearrangement means rearranges the horizontal lines or the horizontal and vertical lines of the image data expanded in the second storage means in a predetermined order. This is because by rearranging the lines, pixels can be arranged so that the continuity of black pixels or white pixels is further improved.

Then, the coding control means transfers the judgment result identification data, the dither data before replacement of the replacement image block and the image data rearranged by the line rearranging means to the coding means.

As a result, each data transferred by the encoding means is compression-encoded (run-length encoding). << Decoding >> In the decoding means, when the determination result identification data, the dither data before replacement of the replacement image block and the compression coding means of the image data rearranged by the line rearranging means are input, Data is decoded (decompressed).

The line rearranging means rearranges the horizontal lines (or the horizontal and vertical lines) of the decoded image data in the original order. This line rearranging means performs the reverse process of the line rearranging means.

Next, the second image block extracting means sequentially extracts image blocks of the same size as the image blocks extracted by the first block extracting means from the image data after the rearrangement processing by the line rearranging means. It

When the decoded determination result identification data indicates that the density change of the input image block is small in the rearrangement means, each pixel of the image data of the image block extracted by the second image block extraction means is selected. Return to the original arrangement. This sort means performs the reverse process of the sort means.

On the other hand, in the case where the decoded determination result identification data in the second replacing means indicates that the density change of the input image block is large, the image of the image block extracted by the second image block extracting means The data is replaced with the dither image data before replacement of the decoded replacement image block.

That is, for each image block, either the processing of the rearranging means or the processing of the second replacing means is alternatively performed according to the determination result identification data of each image block, In this way, the dither image data before the encoding process obtained by dithering the source image data is reproduced.

[0031]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT An embodiment of the present invention will be described below with reference to FIGS.
It will be described based on. FIG. 1 schematically shows the configuration of an encoding / decoding processing device according to an embodiment.

The coding / decoding processing apparatus 100 includes a coding processing unit 10 for coding a pseudo-halftone image obtained by binarizing a multivalued image by dither processing, and compression-coded coded data. And a decoding processing unit 30 for decoding the pseudo halftone image and reproducing the pseudo halftone image.

The encoding processing unit 10 includes a CPU 12 and an RO.
M14, RAM16, scanner 18, dither processing section 20, rearrangement processing section 22 as rearrangement means
And a coding unit 24 as a coding unit, a data output unit 26, an image memory 28, and a coding memory 29.

The above-mentioned components except the CPU 12 are connected to the CPU 12 via the system bus 50.

The CPU 12 is the heart of the encoding processing unit 10 and is a processor that manages the flow of jobs of the above-mentioned components.

The ROM 14 is a memory that stores programs and the like described later, and the RAM 16 is a memory that functions as a work area. In this embodiment, a temporary storage area, a replacement block storage area, an identification data storage area, etc. are provided. The first storage means is configured by this.

The scanner 18 reads a document image and outputs multivalued image data (grayscale image data). For example, a scanner which outputs multivalued image data of 16 gradations is used.

The dither processing unit 20 binarizes (quantizes into binary) the input multi-valued image data by using a predetermined dither matrix having thresholds arranged in a matrix as elements.
To do. That is, the dither processing unit 20 compares the threshold value, which is a constituent element of the dither matrix, with the multi-valued data of each pixel, and, for example, sets a pixel whose data value (density value) is equal to or larger than the threshold value to black (for example, 1), The grayscale image is quantized into a binary value by making the other pixels white (for example, 0) so that the grayscale of the input image can be perceived when viewed in macro. here,
A Bayer type dither matrix is often used.

When the binary data of each block is input, the rearrangement processing unit 22 outputs two pixels of the pixels corresponding to the respective threshold values in the order of the threshold values which are the elements of the dither matrix.
Sort value data.

The encoding unit 24 performs run-length encoding on various input data. As will be described later, the data output unit 26 causes the CPU 12 to generate the code memory 29 when the decoding processing unit 30 of another device requests the code data.
The coded data extracted from is output to the decoding processing unit 30.

The image memory 28 is a memory for storing the image data from the scanner, the image data after the replacement process, and the like. In the present embodiment, the image memory 28 constitutes a second storage means.

The code memory 29 is a memory for storing coded data which has been run length compression coded.

The decoding processing section 30 includes a CPU 32 and an RO.
An M34, a RAM 36, a data input unit 38, a decoding unit 40 as a decoding unit, a printer 42, an image memory 44, a code memory 46, and a sorting processing unit 48 as a sorting unit. Have

The above-mentioned components except the CPU 32 are connected to the CPU 32 via the system bus 60.

The CPU 32 is the heart of the decryption processing unit 30 and is a processor that manages the flow of jobs of the above-mentioned components.

The ROM 34 is a memory that stores programs and the like to be described later, and the RAM 36 is a memory that functions as a work area. In this embodiment, an identification data storage area and the like are provided.

The data input unit 38 receives the data input from the encoding processing unit 10 of another device as described later.

The decoding section 40 decodes (expands) the input coded data into binary data using the same dither matrix as above.

The printer 42 is an image output unit that converts the input binary data into dot information (image information) and prints it out. As the image output means, a CRT display, a liquid crystal panel display or the like which is an image display device may be used instead of the printer 42.

The image memory 44 is a memory for storing the decoded binary image data, and the code memory 46 is a memory for storing the input run-length compression coded data.

The rearrangement processing section 48 reverses the rearrangement processing section 22 to rearrange dots to reproduce the dither image data.

Next, the operation of exchanging data between the encoding / decoding processing apparatuses 100 configured as described above will be described with reference to FIGS. 2 to 7. << Operation of Encoding Processing Unit 10 >> First, the operation regarding the encoding processing of the encoding processing unit 10 of one device will be described with reference to the flowchart of FIG. 2 showing the main control program of the CPU 12. This flow chart starts with
A reading start button (not shown) is pressed, and a command to start reading is issued from the input device (not shown) to the CPU 12
It is when input to.

In step 100, an image is read by the scanner 18, and the multivalued image data output from the scanner 18 is sequentially stored in the image memory 28.

When the image reading is completed, step 1
In step 02, the count value n of the first counter (not shown) for counting block numbers is set to 1 (incremented by 1 from the initial value 0), and in step 104, the block n is read from the multi-valued image data (original image data). (Image block with block number n) is extracted.

In step 106, the maximum density difference C of the extracted block n (difference between the maximum density value and the minimum density value of the pixels in the block) C is calculated, and the flow advances to step 108 to dither the multivalued image data of the block n. The data is transferred to the processing unit 20 and the dither processing of block n is performed. Here, the dither processing unit 2
When 0, the dither matrix stored in the ROM 14 having the same size as the block size, for example, 4 × 4 pixel size is used to compare the threshold value, which is an element of the dither matrix, with the density value of each pixel. To convert. The dither image data (monochrome binary data) thus obtained is stored in the temporary storage area of the RAM 16.

In step 110, it is determined whether the maximum density difference C calculated in step 106 is less than or equal to a predetermined threshold value P. If the determination is affirmative, the process proceeds to step 112 to temporarily store in the RAM 16. The rearrangement processing unit 2 processes the dither image data of the block n stored in the area.
Transfer to 2. As a result, the rearrangement processing unit 22 rearranges the dots of the dither image as follows. That is, in the rearrangement processing unit 22, the threshold values which are the constituent elements of the Bayer type dither matrix as shown in FIG. 8A are arranged in the order of size as shown in FIG. 8B. The pixels corresponding to the threshold are rearranged. Here, when the dots of the dither image are rearranged by the rearrangement processing unit 22, black pixels tend to be arranged in the upper part of the image block, and white pixels tend to be arranged in the lower part of the image block. The data after this rearrangement processing is transferred to and stored in the image memory 28 by a DMA controller (not shown).

In the next step 114, "1" is set as the rearrangement determination code data (determination result identification data) of the block n and stored in the identification data storage area of the RAM 16, and then the process proceeds to step 122.

On the other hand, if the determination in step 110 is negative, the process proceeds to step 116, and the dither image data of the block n stored in the temporary storage area of the RAM 16 is stored in the image memory 28 one before. Block n-1 is replaced with a block having the same pattern. This replacement is performed by moving the dither image data of the block n stored in the temporary storage area of the RAM 16 to the replacement block storage area of the RAM 16 and then copying the data of the block n-1 in the image memory 28 to temporarily store the data in the RAM 16. This is done by storing in the storage area. This replacement is performed as it is because the replacement block n to be replaced has a pattern in which the maximum density difference in the block is large and the pattern is completely different from the surrounding blocks (blocks in which the dots are rearranged). Then,
This is because there is a high possibility that the run length will be cut off during the line rearrangement processing that is performed later.

In the next step 118, the block n after replacement is stored in the storage area of the block n of the image memory 28, and the process proceeds to step 120 where "0" is set as the rearrangement determination code data (determination result identification data) of the block n. Is set and stored in the identification data storage area of the RAM 16, and then the process proceeds to step 122.

In step 122, the first counter for counting the block number is incremented by 1, and in step 124
And the block number n is the total number N of blocks in the input image.
If it is judged to be larger than this, and this judgment is denied,
Returning to step 104, the above-mentioned processing and judgment are repeated.

In this way, the dot rearrangement process or the block replacement process is completed for all the input image blocks, and when the determination in step 124 is affirmed, the lines of the replacement image in step 126 are rearranged. Move to a subroutine. At this time, the image memory 28
Image data after dot rearrangement processing or block replacement processing is stored and expanded in the order of block numbers. The image developed in the image memory 28 will be referred to as a "replacement image" for convenience hereinafter.

In the subroutine for rearranging the lines of the replacement image, as shown in FIG.
The parameter i is set to "1" at 00, and step 202
The parameter k corresponding to the line number of the image after line rearrangement (this image is referred to as “rearranged image 1” for convenience) is set to “1”.

In the next step 204, it is judged whether or not i ≦ m (m: the number of rows of the dither matrix = the number of columns of the dither matrix) is satisfied, and if this judgment is affirmed, the routine proceeds to step 206. After setting "0" to the parameter j, in step 208, the line number s of the replacement image before line rearrangement is calculated by the formula of s = m × j + i.
For example, dither matrix size = block size is 4
In the case of x4, if i = 1 and j = 0, then m = 4 and s = 4 × 0 + 1 = 1.

At the next step 210, it is judged whether or not s ≦ M (M: the total number of lines in the input image) is satisfied. If this judgment is affirmed, the process proceeds to step 214 and the line s of the replacement image is set. Is copied to the line k of the rearranged image 1. That is, in the image memory 28, an area (referred to as "area 1") for expanding the rearranged image is provided separately from an area for expanding the replacement image (referred to as "area 1" for convenience). The data of the line s of the replacement image is copied to the line k portion of the area 2. For example, line 1 of the replacement image is copied to line 1 of the reordered image.

Next, the parameters k and j are each incremented by 1 (steps 216 and 218), and the process returns to step 208 to repeat the above-described processing determination.

On the other hand, if the determination in step 210 is negative, the process proceeds to step 212 and the parameter i
Is incremented by 1, and then the process returns to step 204 to repeat the above processing / judgment. For example, m = 4, j = 2
If i = 1, M = 8 and s = 4 × 2 + 1 = 9, the determination at step 210 is denied.

On the other hand, if the determination in step 204 is negative, the process of this subroutine is terminated and the process returns to the calling source, and the process proceeds to the subroutine for rearranging the columns of the rearranged image 1 shown in step 128 of the main routine. To do. If the block size is 4x4,
When the parameter i = 5, the determination at step 204 is denied.

When the line rearrangement processing is performed by the above subroutine when the size of one block is 4 × 4 and the total number of lines is 8, the rearrangement of lines is performed as shown in FIG. 9A. Is done.

In the subroutine for rearranging the columns of the rearranged image 1, as shown in FIG. 4, first, in step 300, the parameter i is set to "1", and then step 30
In step 2, the parameter r corresponding to the column number of the column rearranged image (this image is referred to as “rearranged image 2” for convenience) is set to “1”.

At the next step 304, it is judged whether or not i ≦ m (m: the number of rows of the dither matrix = the number of columns of the dither matrix) is satisfied. If this judgment is affirmed, the routine proceeds to step 306. After setting “0” to the parameter p, in step 308, the column number q of the rearranged image 1 before column rearrangement is calculated by the formula of q = m × j + i.

In the next step 310, it is judged whether or not q≤U (U: the total number of columns in the input image) is satisfied, and if this judgment is affirmed, the routine proceeds to step 314. The column q is copied to the column r of the rearranged image 2. That is, the column q of the rearranged image 1 stored in the area 2 is stored in the column r of the area 1 in the image memory 28.
The data of is copied.

Next, the parameters r and p are each incremented by 1 (steps 316 and 318), and the process returns to step 308 to repeat the above process determination.

On the other hand, if the determination in step 310 is negative, the process proceeds to step 312 and the parameter i
Is incremented by 1, and then the process returns to step 304 to repeat the above processing / judgment. For example, m = 4, p = 4
If i = 1, U = 16 and q = 4 × 4 + 1 = 17, the determination at step 310 is denied.

On the other hand, when the determination in step 304 is negative, the processing of this subroutine is terminated and the process returns to step 130 of the main routine. When the block size is 4 × 4, the determination at step 304 is denied when the parameter i = 5.

When the column rearrangement process is performed by the above subroutine when the size of one block is 4 × 4 and the total number of columns is 16, line arrangement is performed as shown in FIG. 9B. Replacement is done.

In step 130 of the main routine, the rearranged image 2 stored in the area 1 in the image memory 28 is sorted.
Is run-length compressed and encoded by the encoding unit 24, and in step 132, the dither data before replacement of the replacement block stored in the replacement block storage area of the RAM 16 is run-length compression-encoded by the encoding unit 24. In step 134, the rearrangement determination code data string stored in the identification data storage area of the RAM 16 is run-length compression-encoded using the encoding unit 24, and then a series of processes is ended. Here, each coded data compression-coded by the coding unit 24 is transferred to and stored in the code memory 29 by a DMA controller (not shown). << Operation of Decoding Processing Unit >> Next, the operation relating to the decoding of the decoding processing unit 30 of the other device will be described with reference to the CPU 32 of FIG.
This will be described along with a flowchart showing the main control program of. As a premise, a decoding start button (not shown) is pressed, a decoding instruction command is input from an input device (not shown), and the CPU 32 requests a code data via the data input unit 38 to the coding processing unit 10 of one device. The encoded data in the code memory 29 is sequentially output via the data output unit 26 by the CPU 12 on the side of the encoding processing unit 10, and this data is stored in the code memory 46 via the data input unit 38. Be present. Here, the compressed data is stored in the code memory 46 in a predetermined order, for example, the image data, the dither data before replacement of the replacement block, and the identification data, and the CPU 32 stores each data based on this storage order. Can be identified.

First, the compression-encoded data of the rearranged image 2, the dither data before the replacement of the replacement block, and the rearrangement determination code data stored in the code memory 46 are sequentially decoded by the decoding unit 40. (Stretch).
(Step 400, Step 402, Step 40
4). The decoded data is transferred to and stored in the image memory 44 and the identification data storage area of the RAM 36 by a DMA controller (not shown).

When the decoding of the respective data is completed, the routine proceeds to a subroutine of step 406 for rearranging the columns of the rearranged image 2.

In the subroutine for rearranging the columns of the rearranged image 2, as shown in FIG. 6, first, in step 500, the parameter i is set to "1", and then step 5 is executed.
In 02, the parameter q corresponding to the column number of the rearranged image 1 obtained by rearranging the columns of the rearranged image 2 in the original order is set to “1”.

At the next step 504, it is judged whether or not i ≦ m (m: the number of rows of the dither matrix = the number of columns of the dither matrix) is satisfied. If this judgment is affirmed, the routine proceeds to step 506. After setting “0” to the parameter p, the column number r of the rearranged image 2 is calculated by the equation r = m × p + i in step 508.

At the next step 510, it is judged whether or not r ≦ U (U: the total number of columns in the input image) is satisfied. If this judgment is affirmed, the routine proceeds to step 514 and the rearranged image 2 The column q is copied to the column r of the rearranged image 1. That is, the data of the column q of the rearranged image 2 stored in the other area (for convenience, referred to as “area 1”) is copied to the column r portion of the area (for convenience, referred to as “area 2”) in the image memory 44. To do.

Next, the parameters q and p are each incremented by 1 (steps 516 and 518), and the process returns to step 508 to repeat the above-described processing / judgment.

On the other hand, if the determination in step 510 is negative, the process proceeds to step 512 and the parameter i
Is incremented by 1, and then the process returns to step 504 to repeat the above processing / judgment. For example, m = 4, p = 4
If i = 1, U = 16 and r = 4 × 4 + 1 = 17, the determination at step 510 is denied.

On the other hand, if the determination in step 504 is negative, the processing of this subroutine is terminated and the process returns to the calling source, and the subroutine for rearranging the lines of the rearranged image 1 shown in step 408 of the main routine is entered. Transition. When the block size is 4 × 4, the determination at step 304 is denied when the parameter i = 5.

When the column rearrangement processing is performed by the above subroutine when the size of one block is 4 × 4 and the total number of columns is 16, the column in the direction opposite to the arrow in FIG. Sorting is done.

In the subroutine for rearranging the lines of the rearranged image 1, as shown in FIG. 7, first, in step 600, the parameter i is set to "1", and then step 60 is executed.
In step 2, "1" is set to the parameter s corresponding to the line number of the replacement image obtained by rearranging the lines of the rearranged image 1 in the original order.

At the next step 604, it is judged whether or not i ≦ m (m: the number of rows of the dither matrix = the number of columns of the dither matrix) is satisfied. If this judgment is affirmed, the routine proceeds to step 606. After setting “0” to the parameter j, in step 608, the line number k of the rearranged image 1 before line rearrangement is calculated by the equation of k = m × j + i. For example, if the dither matrix size = the block size is 4 × 4, and i = 1 and j = 0, then m =
Since it is 4, k = 4 × 0 + 1 = 1.

At the next step 610, it is determined whether or not k ≦ M (M: the total number of lines in the input image) is satisfied. If the determination is affirmative, the process proceeds to step 614 and the rearranged image 1 is sorted. Copy line s to line k of the replacement image. That is, the data of the line s of the rearranged image 1 is copied to the line k portion of the area 2 in the image memory 44. For example, line 1 of rearranged image 1 is copied to line 1 of the replacement image.

Next, the parameters s and j are each incremented by 1 (steps 616 and 618), and the process returns to step 608 to repeat the above-described processing / judgment.

On the other hand, if the determination in step 610 is negative, the process proceeds to step 612 and the parameter i
Is incremented by 1, and then the process returns to step 604 to repeat the above processing / judgment. For example, m = 4, j = 2
If i = 1, M = 8 and k = 4 × 2 + 1 = 9, then the determination at step 610 is denied. On the other hand, when the determination in step 604 is negative, the processing of this subroutine is ended and the processing returns to step 410 of the main routine. When the block size is 4 × 4, the determination in step 604 is denied when the parameter i = 5.

If the line rearrangement process is performed by the above subroutine when the size of one block is 4 × 4 and the total number of lines is 8, the lines in the direction opposite to the arrow in FIG. Sorting processing is performed.

After the count value n of the second counter for counting the number of image blocks is set to "1" in step 410 of the main routine, the image memory 44 is set in step 412.
Block n from the replacement image data stored in
Image data is extracted and stored in the temporary storage area of the RAM 36.

At the next step 414, it is determined whether the rearrangement determination code of the block n stored in the identification data storage area of the RAM 36 is "1", and the rearrangement determination code is "0". Is denied, the process proceeds to step 418 to replace the block n of the replacement image with the dither data before replacement of the replacement image block n stored in the image memory 44.

On the other hand, if the determination in step 414 is positive, the process proceeds to step 416 to transfer the replacement image data of block n to the rearrangement processing unit 48. As a result, the sorting processing unit 22 described above in the sorting processing unit 48 is performed.
The dot rearrangement processing opposite to that is performed, and the dither image of the block n is reproduced.

Then, in step 420, step 4
The dither data of the block n rearranged in 16 or the dither data of the block n replaced in step 418 is output to the printer 42.

In the next step 422, the second counter for counting the number of image blocks is incremented by 1, and in the next step 424, it is judged whether or not n> N. If this judgment is denied, step 412 Then, the above process and judgment are repeated.

In this way, when the decoding and output processing of the image data of all blocks in the input data is completed, the determination at step 424 is affirmed and the series of decoding processing is completed.

At the end of this decoding process, the dither image data of all image blocks are stored in the memory of the printer 42 in the same state as when the encoding was started by one of the devices, and the dot data was stored in one line. Alternatively, it is printed out for each predetermined line, and a pseudo halftone image is finally obtained.

According to the encoding / decoding processing apparatus 100 of the present embodiment described above, for example, the dither matrix in the dither processing unit 20 is Ba as shown in FIG.
Step 10 using the yer type 4x4 size
Assuming that 8 blocks of dither image data as shown in FIG. 10A are obtained as a result of performing the dithering process of 8, the image memory 28 is stored in the image memory 28 by repeating the processes of steps 110 to 122. The replacement image data of 8 blocks as shown in FIG. Note that, in FIG. 10B, the replacement image data is shown as the black and white binary image data, but the data of 0 and 1 is actually stored.

In FIGS. 10A and 10B, the portion surrounded by a thick line visually shows the block replacement processing performed in steps 116 to 118. In this case, the replacement block in the RAM 16 is replaced. The dither data before replacement of the replacement block as shown in FIG. 10C is stored in the storage area. Here, this replacement process is performed by executing block rearrangement (dot rearrangement) on the dither image, in which black pixels are at the upper part of the image block and white pixels are at the lower part of the image block. However, if the dots are rearranged in the same manner as the other blocks, the dither image data in the fourth column (data in the bold line frame) shown in FIG. Since it is highly likely that the run length that has been lengthened by the dot rearrangement process will be cut off, dither data for such blocks can be replaced with other neighboring blocks without rearranging the dots, and This is because it becomes possible to lengthen.

In the case of this example, the rearrangement determination code data is set as shown in FIG. 10D (step 114, step 120).

Next, the lines of the replacement image data shown in FIG. 9A are rearranged (step 12).
6). The rearrangement of this line is performed as follows.

That is, first, the line 1 in the replacement image is copied to the line 1 in the rearranged image 1. Next, the line 5 in the replacement image (that is, the line 1 of the second block row of the dither block row that is continuous in the horizontal direction) is copied to the line 2 in the rearranged image 1. Next, the line 2 in the replacement image is copied to the line 3 in the rearranged image 1, and then the line 6 in the replacement image (that is, the line 2 of the second block row in the dither block row that is continuous in the horizontal direction) is copied. Copy to line 4 in rearranged image 1. In the same manner, line 3 in the replacement image is changed to line 5 in the rearranged image 1, line 7 in the replacement image is changed to line 6 in the rearranged image 1, line 4 in the replacement image is changed.
To the line 7 in the rearranged image 1 and finally the line 8 in the rearranged image to the line 8 in the rearranged image 1 to end the line rearrangement process (see FIG. 3). As a result of this line rearrangement processing, FIG.
Image data of the rearranged image 1, that is, image data in which lines 1 of each block of the replacement image, lines 2 of lines, lines 3 of lines, and lines 4 of adjacent blocks are obtained. Lines having the same black-and-white pattern tend to be adjacent to each other, and both the black run and the white run are long, as shown in FIGS.
It can be clearly seen from the comparison with (A).

Next, the column rearrangement process of the rearranged image 1 shown in FIG. 9B is performed (step 12).
8). This column rearrangement process is performed as follows. That is, first, the column 1 in the rearranged image 1 is copied to the column 1 in the rearranged image 2. Next, the column 5 in the rearranged image 1 (that is, the column 1 of the second block row in the dither block row that is continuous in the vertical direction) is copied to the column 2 in the rearranged image 2. Next, the column 9 in the rearranged image 1 (that is, the column 1 of the third block row in the dither block row that is continuous in the vertical direction) is copied to the column 3 in the rearranged image 2, and then the column in the rearranged image 1 is copied. 13 (that is, 4 of the dither block row that is vertically connected)
Copy column 1) of the th block row to column 4 in rearranged image 2. Similarly, the rearrangement process is performed so that the columns 2, 3, and 4 in each block row are adjacent to each other (see FIG. 4). As a result of this column rearrangement process, FIG.
Data of the rearranged image 2, that is, image data in which columns 1 of each block of the rearranged image 1, columns 2 of each other, columns 3 of each other, and columns 4 of each block are adjacent to each other are obtained. It can be seen from the comparison between FIGS. 11A and 11B that the columns having the same black-and-white pattern tend to be adjacent to each other, and both the black run and the white run are longer.

Therefore, in step 130, the rearranged image 2
When run length compression is performed, the compression coding efficiency becomes very high.

On the other hand, on the decoding side, the decoding unit 40 first decodes the compressed data of the rearranged image 2, the dither data before the replacement of the replacement block, and the compressed data of the rearrangement determination code string (step 400, step 402). , Step 404), image memory 4 respectively
4, stored in the identification data storage area of the RAM 36.

After the decoding is completed, the column rearrangement process and the line rearrangement process of the rearranged image 2 in the image memory 44 are sequentially carried out in the reverse order to that carried out on the encoding side (steps 406 and 408). . The column / line rearrangement processing is completed, and the replacement image is stored in the image memory 4.
4, the replacement image is read in block units, and if a block that needs replacement is encountered, that block is replaced with the dither data before replacement of the replacement block stored in the image memory 44 (step 418), when a block requiring dot rearrangement is encountered, the data of that block is transferred to the rearrangement processing unit 48 to perform dot rearrangement (step 416), and the original dither is performed for each block. The data is restored, and this is sequentially output to the printer 42. It should be noted that the determination as to whether the block should be replaced or the block in which dots are to be rearranged is determined based on the rearrangement determination code of the block stored in the identification data storage area of the RAM 36. That is, if the rearrangement determination code corresponding to the block of interest at present is 0, it is replaced, and if it is 1, the dots are rearranged.

When such processing is executed for all blocks, the dither data of the restored image is completed in the memory of the printer 42 and is printed out, so that the original dither data is directly printed out. It is possible to obtain a decoded image with good image quality equivalent to

As is clear from the above description, in the present embodiment, the first block extracting means, the judging means, the first replacing means, the storage controlling means, the line rearranging means and the encoding controlling means are the CPU 12's. Realized by function,
It can be seen that the line rearranging means, the second image block extracting means, and the second replacing means are realized by the function of the CPU 32.

In the above embodiment, the coding / decoding processing device has been described. However, considering a coding processing device having the same configuration as the coding processing unit 10, the effect of improving the compression efficiency at the time of coding is obtained. It goes without saying that you can achieve it.

Further, in the above embodiment, the case where the replacement image data is suddenly obtained from the dither image data has been exemplified, but the dither image data as shown in FIG. 10A is rearranged as shown in FIG. After obtaining the image data, one of the blocks in which the sorting process is performed only on the blocks in which the sorting process of the dots in this sorting image data has not been performed (the blocks surrounded by the thick line frame in the figure) Of course, the replacement image data may be obtained by replacing with the data of the same pattern. Such a thing can be easily realized by changing the software.

Further, in the above embodiment, the case where the column rearrangement process of the rearranged image 1 obtained by this is executed after the line rearrangement process of the replaced image is exemplified, but only the line rearrangement process of the replaced image is performed. Even if only the process of rearranging the lines of the decoded rearranged image 1 in the original order is performed at the time of decoding, the image obtained after the decoding is performed. It is possible to improve the coding efficiency as compared with the conventional example without causing the deterioration of the image quality.

The encoding / decoding processing device of the present invention is
Specifically, the present invention can be applied to a data filing system, a facsimile machine, and the like. For example, in the case of being applied to a facsimile machine, it is shared among the components of the encoding processing unit 10 and the decoding processing unit 30. It is desirable to share the possible constituent elements as much as possible, and it is sufficient to provide one CPU without providing two CPUs. Further, in this case, the encoding unit and the decoding unit are configured as an encoding / decoding unit, the data input unit and the data output unit are a modem, and the N
It is desirable that the CU or the like be used in common.

On the other hand, when applied to a data filing system, the encoded data output from the data output section is temporarily stored in a magnetic disk, an optical file, etc., and the data is stored from these storage means via the data input section. The configuration is such that it is read out, and data is exchanged within the same device.

In the above embodiment, the case where the coded data is once stored in the RAM has been illustrated. However, in a facsimile machine or the like, the coded data can be obtained by performing the coding and the line connection work in parallel. It can be immediately transmitted to the other device via the communication line.

Further, in the above embodiment, for the sake of convenience of description, the case where the direct memory access by the DMA controller is used only partially is illustrated, but the data transfer between most of the hardware modules is performed by the direct memory access by the DMA controller. Maybe,
By doing so, it becomes possible to further improve the data processing speed.

[0117]

As described above, according to the encoding processing apparatus of the first aspect, not only the rearrangement of the pixels (dots) by the rearrangement means but also the change in the light and shade that is not the target of the rearrangement processing are performed. With respect to a large image block, the replacement means replaces the image block with a small change in shading with the data, and the rearrangement processing and the rearrangement of the lines of the image data obtained by the replacement processing are performed by the line rearrangement means. Since the compression encoding is performed by the encoding means after that, the compression efficiency at the time of data encoding is improved as compared with the case of the conventional example in which the encoding is simply performed after the dot rearrangement processing of each block. There is an unprecedented excellent effect that it can be further improved.

According to the encoding / decoding processing device of the second aspect, the encoding is performed in the same manner as the invention of the first aspect, and at the time of decoding, the line rearranging means rearranges the lines. After the processing, pixel rearrangement processing or block replacement processing is performed for each block based on the decoded determination result identification data, and as a result, the original dither image data can be decoded. There is an effect that the compression efficiency at the time of data encoding can be further improved without deteriorating the image quality of an image obtained later.

[Brief description of drawings]

FIG. 1 is a block diagram schematically showing a configuration of an encoding / decoding processing apparatus according to an embodiment.

FIG. 2 is a flowchart showing a main control program of a CPU which constitutes the encoding processing unit of FIG.

FIG. 3 is a flowchart showing a subroutine for rearranging the lines of the replacement image of FIG.

FIG. 4 is a flowchart showing a subroutine for rearranging the columns of the rearranged image 1 in FIG.

5 is a flowchart showing a main control program of a CPU which constitutes the decoding processing unit of FIG. 1. FIG.

FIG. 6 is a flowchart showing a subroutine for rearranging the columns of the rearranged image 2 in FIG.

7 is a flowchart showing a subroutine for rearranging the lines of the rearranged image 1 in FIG.

FIG. 8 is a diagram for explaining a rearrangement principle of a rearrangement processing unit.

9A is a diagram showing an example of line rearrangement processing of a replacement image performed according to the flowchart of FIG. 3;
(B) is a diagram showing an example of a column rearrangement process of the rearranged image 1 performed according to the flowchart of FIG. 4.

FIG. 10 is a diagram for describing dither processing and block replacement processing in the encoding processing unit.

11A and 11B are diagrams visually showing data obtained by main processing by the encoding processing unit, FIG. 11A showing an example of a rearranged image 1 obtained by line rearrangement processing, and FIG. FIG. 6 is a diagram showing an example of a rearranged image 2 obtained by a column rearrangement process.

FIG. 12 is a diagram for explaining a modified example of the above-described embodiment, showing an example of rearranged image data obtained by rearranging dots only in an image block in which dither image data has a small change in shading.

FIG. 13 is a diagram for explaining a conventional encoding processing method.

[Explanation of symbols]

12 CPU (first block extraction means, determination means, first replacement means, storage control means, line rearrangement means, coding control means) 16 RAM (first storage means) 20 Dither processing unit (dither processing means) ) 24 encoding unit (encoding means) 22 rearrangement processing unit (rearranging means) 28 image memory (second storage means) 32 CPU (line rearrangement means, second image block extraction means, second replacement) Means) 40 Decoding unit (Decoding means) 48 Reordering processing unit (Reordering means) 100 Encoding / decoding processing device

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification code Office reference number FI technical display location H03M 7/30 Z 9382-5K

Claims (2)

[Claims] 1. A coding processing device comprising a coding means for compressing and coding image data, comprising block extraction means for sequentially extracting image blocks of a predetermined size from grayscale image data, and each of the extracted images. Determining means for determining the magnitude of the shade change of the block; dither processing means for dithering each image block extracted by the block extracting means using a predetermined dither matrix to convert it into dither image data; For the image block determined to have a small change in shading, the dither image data is rearranged into binary data in which each pixel data is rearranged in the order of the threshold value which is an element of the dither matrix. For the replacement image block determined to have a large change in shading by the determination means, Replacement means for replacing the user image data with binary data of one of the blocks rearranged by the rearrangement means, first and second storage means for storing image data, and the replacement The dither data before replacement of the image block is stored in the first storage means and the binary data of the image block rearranged by the rearranging means and the binary data of the image block rearranged by the replacing means. And a storage control means for storing and developing in the second storage means, and a horizontal line or horizontal and vertical lines of the image data expanded in the second storage means arranged in a predetermined order. Line rearrangement means for changing, dither data before replacement of the replacement image block stored in the first storage means, and the line arrangement Encoding apparatus having an encoding control means for transferring image data to said encoding means after being sorted by the example section. 2. A coding / decoding processing device comprising a coding means for compressing and coding image data and a decoding means for decoding the coded data, wherein an image block of a predetermined size is generated from the grayscale image data. First block extraction means for sequentially extracting, determination means for determining the size of the change in grayscale of each of the extracted image blocks and creating determination result identification data indicating the determination result, and the block extraction means for extracting Dither processing means for converting each image block into dither image data by dithering it using a predetermined dither matrix; and for the image block judged to have a small change in shading by the judging means, the dither of the image block The image data is converted into binary data in which each pixel data is rearranged in the order of the size of the threshold value which is an element of the dither matrix. Reordering means, and for the replacement image block determined by the determining means to have a large change in shading, the dither image data of the image block is one of the blocks that have been rearranged by the rearranging means. First replacement means for replacing the replacement image block with the binary data, first and second storage means for storing image data, and dither data before replacement of the replacement image block is stored in the first storage means. Storage control means for storing the image block data rearranged by the rearranging means and the image block data rearranged by the replacing means in the second storing means and expanding the same; A line for rearranging the horizontal lines or the horizontal and vertical lines of the image data developed by the means in a predetermined order. A rearrangement means, an encoding control means for transferring the determination result identification data, the dither data before the replacement of the replacement image block and the image data rearranged by the line rearrangement means to the encoding means; The first block from the line data rearrangement means for rearranging the horizontal lines or the horizontal and vertical lines of the image data in the original order, and the image data after the rearrangement processing by the line rearrangement device. Second image block extracting means for sequentially extracting image blocks of the same size as the image block extracted by the extracting means, and the decoded determination result identification data indicates that the density change of the input image block is small. Each pixel of the image data of the image block extracted by the second image block extracting means is arranged in the original arrangement. When the decoded determination result identification data indicates that the density change of the input image block is large, the image data of the image block extracted by the second image block extracting unit is returned. And a second replacement unit that replaces the decoded replacement image block with the dither image data before replacement.