JP2811469B2 - Information processing device with pseudo halftone image processing function - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a personal computer, an image workstation, an image filling system,
The present invention relates to an improvement of an information processing apparatus having various image processing functions capable of processing digital images by a facsimile apparatus and other micro computer controls, and more particularly, to a pseudo halftone image binarized by a dither method or the like. When encoding and compressing, the image is converted into an image that can utilize the features of the run-length encoding method in advance, thereby enabling high compression processing of the pseudo halftone image and using the information storage device in an image filling system or the like. The present invention relates to an information processing apparatus having improved efficiency and system performance.

More specifically, by improving the use efficiency of disks (FD, HD, OD, etc.), which is a problem when storing pseudo halftone images, it is possible to achieve a high compression ratio of pseudo halftone images. The present invention relates to an information processing apparatus having improved system performance.

2. Description of the Related Art Information processing apparatuses such as personal computers and image workstations having a function of processing a pseudo halftone image binarized by a dither method or the like are conventionally known.

In such a conventional information processing apparatus, when storing the read original image data, when the data amount of the compressed data is larger than the data amount of the non-compressed data as in a pseudo halftone image, a normal Like a binary image, it is compressed or uncompressed data is held as it is.

However, if the pseudo halftone image binarized by the dither method is compressed by the run-length encoding method in the same manner as a normal binary image, the code amount after the compression becomes very large, so that the compression ratio becomes large. Becomes extremely large, and as a result, the compression time becomes long.

The cause is that the run-length encoding method is an image compression method on the assumption that "a certain dot has a relation with dots around it".
The pseudo halftone image binarized by the dither method is M × N
This is because the matrix consisting of (dots) is one pixel, so that there is a correlation between adjacent matrices, but there is no relationship between adjacent dots.

First, a dither image which has been conventionally used will be described as an order of explanation.

A dither image consists of one pixel, each of M × N (dot)
And a pseudo-halftone image is created for each reference unit by a dither pattern having a basic configuration for expressing a halftone density.

Therefore, the dither pattern will be described in detail with reference to the drawings.

FIGS. 6 (1) to (10) show that the configuration of one pixel is 4
It is a figure which shows an example of the dither pattern formed from * 4 (dot). In the drawing, the numbers indicate the order of dots that are set to "black" in correspondence with the gradation.

As shown in FIGS. 6 (1) to (10), one pixel has four pixels.
A dither pattern of 16 gradations formed from × 4 (dots) has a dither pattern of 16 (= 4 × 4) according to the number of dots to be “black”.
The gradation density can be expressed.

The dither patterns include a Bayer type as shown in FIG. 6 (1), a primary halftone type as shown in FIG. 6 (2), a spiral type as shown in FIG. 6 (3), and a dither pattern as shown in FIG. ), A spiral type deformation as shown in FIGS. 6 (5) and (6), a directionality type deformation as shown in FIG. 6 (7), and FIG. 6 (8).
Attention is focused on patterns of levels 4, 8, and 12 as in (10), and several types of shapes that naturally connect them are known.

That is, as shown in FIGS. 6 (1) to (10), in the case of a 16-gradation dither image, one pixel is represented by 4.times.4 (dots), so that the image is slightly coarse, but black dots are obtained. By changing the number in the order of the number corresponding to the gradation, it appears to the human eye that there is shading, so that it is possible to express a halftone image.

As shown in FIGS. 6 (1) to (10), how to assign the threshold number of the density level to 4 × 4 (= M × N) dots in one matrix is determined by the pseudo half tone. There are various types of expression methods, but in all methods, the numbering method for each matrix is unified.

As described above, one pixel is formed of 4 × 4 (dots), and the dots at each dot position are black dots in the order of the numbers, whereby the density of 16 gradations can be expressed.

In the dither image, one pixel is 4 × 4 (dots).
This dither pattern allows a multi-valued image such as a photograph to be represented as a pseudo-halftone image.

When such a dither image is read by a scanner or the like in an image data processing system such as a personal computer capable of processing digital images by micro computer control or the like, a scanner having a dither image reading function is used. Then, at the time of reading, the reading of the dither image may be designated.

FIG. 7 is a functional block diagram showing an example of a main configuration of an information processing apparatus having a conventional pseudo halftone image processing function. In the drawing, 11 is a CPU, 12 is a main memory, 13 is a floppy disk drive (FDD)
Unit, 14 is HDD (Hard Disk Drive) unit, 15 is code memory, 16 is optical disk, 17 is graphics controller, 18 is image compression / decompression controller, 19 is image memory, 20 is CRT display, etc. The apparatus, 21 is an image scanner, 22 is a printer, 23 is a system bus, and 24 is an image bus.

In the block diagram shown in FIG. 7, a CPU 11 is a central processing unit for managing and controlling the entire system.

The main memory 12 stores information used for controlling a system including a RAM and a ROM.

The FDD unit 13 is a kind of external storage means having a function of driving a floppy disk for storing necessary data.

The HDD unit 14 is also a kind of large-capacity external storage means composed of a hard disk.

The code memory 15 is a memory that stores run-length encoded image data.

The optical disk 16 is also a kind of large-capacity external storage means.

The graphics controller 17 has a function of editing the image memory 19 at the subsequent stage according to a command given from the CPU 11.

The image compression / decompression controller 18 has a function of run-length encoding the image data stored in the image memory 19 and converting the run-length encoded data stored in the code memory 15 into original image data. ing.

The image memory 19 is a bitmap type memory for storing image data.

The display device 20 such as a CRT display is a bitmap type display means for visualizing image data.

The image scanner 21 is capable of inputting a pseudo halftone image by a dither pattern, and stores the read image data in the image memory 19 via the image bus 24.

The printer 22 is a heat-sensitive or other printing means for creating a hard copy with a dot image, and receives image data from the image memory 19 via the image bus 24.

An information processing apparatus for compressing and encoding pseudo halftone image data and storing the data is configured as shown in FIG.

However, as described above, the run-length encoding method is not very effective as a compression method of the pseudo halftone image binarized by the dither method, and as a result, as described above, the compression ratio is extremely high. There are many disadvantages, such as the size and the compression time being longer.

According to the present invention, when such a disadvantage in a conventional information processing apparatus, that is, when a pseudo halftone image binarized by a dither method is compressed, a run-length encoding method is used as it is, The compression time is long and the compression ratio is extremely poor. After converting the pseudo halftone image into image data that can utilize the features of the run-length encoding method, and then performing image compression by run-length encoding on the image data, By providing a specific conversion / generation means for extracting the binarized pseudo-halftone image for each pixel at the same position in the dither matrix and converting / generating the image to a highly correlated image, It is another object of the present invention to provide an information processing apparatus that enables image processing with a high compression ratio.

Means for Solving the ProblemsIn the present invention, at least, an image input means for converting a halftone image into digital information by dithering or the like, display means, memory means, and a central processing unit such as a CPU, M × N
In an information processing system having an image processing function including a compression process of a binarized pseudo halftone image by a dither method or the like using a pixel region of A pixel area dividing means for dividing the matrix area into M × N pixel areas, and reading the divided halftone image data of the divided M × N pixel areas by multiplying the raster width of the page by N times A first data reading means, a data rotating means for rotating the data read from the first data reading means by 90 °, and a data rotating means for increasing the raster width by a factor of M for the data rotated by the data rotating means. 2 in the main scanning direction and sub-scanning direction for each pixel at the same position in the dither matrix for the pseudo halftone image of one page read from the second data reading means. An image generating means for generating M × N images extracted and thinned out to 1 / (M × N) of the original image, and a run for performing run-length encoding on the image generated by the image generating means In the compression processing of the pseudo halftone image binarized by the dither method or the like, before the run-length encoding, the image generation means converts the original image into M × N images. The image is converted and generated, and run-length encoding is performed on the generated image.

Next, an embodiment of an information processing apparatus having a pseudo halftone image processing function of the present invention will be described in detail with reference to the drawings.

First, a specific example of the basic principle of the compression process of the pseudo halftone image by the information processing apparatus of the present invention will be described for easy understanding.

In the following example, the configuration of the dither matrix is
The case of 4 × 4 (dots) will be described.

As already explained in connection with FIGS. 6 (1) to (10), how to assign the threshold number of the density level to 4 × 4 (= M × N) dots in one matrix There are various methods for expressing pseudo-halftones, but in all methods, the numbering method for each matrix is unified.

Therefore, in any of the pseudo halftone images of any of the methods, the densities of adjacent matrices are generally very similar except for a pattern portion such as a direct pattern or a curve.

The information processing apparatus of the present invention focuses on such a feature of the pseudo halftone image, and converts the original image data into an image obtained by thinning out each pixel at the same position of the pseudo halftone image so that the feature can be fully utilized. The image data is converted, and run-length encoding is performed on the converted image data.

FIG. 2 is a diagram showing a state of dither matrix before image conversion.

In FIG. 2, numerals 1 to 16 are assigned to each pixel in the matrix of the 4 × 4 configuration, and alphabets “a to l” are assigned to the numerals to distinguish the 16 matrices. The correspondence between pixels in the matrix is clarified.

As shown in FIG. 2, from a pseudo halftone image binarized by the dither method, a 4 × 4 (generally M ×
N) 4 × 4 (M × N) images extracted in the main scanning and sub-scanning directions are generated for each element of the dither matrix
Run-length encoding is performed on the generated image.

In FIG. 2, the pseudo halftone image for one page is horizontally transformed from the pseudo halftone image so that the basic principle of the compression process of the pseudo halftone image in the information processing apparatus of the present invention can be easily understood. This figure shows a case where the image is composed of a total of 12 (= 3 × 4) pixels for three pixels and four pixels of the pseudo halftone image as in the vertical direction.

However, in actual one page, P (>> 3) pixels of the pseudo halftone image in the horizontal direction and Q of the pseudo halftone image in the vertical direction.
(>>>> 4) pixels, and it is needless to say that the number of pixels is not so small, but the basic principle is exactly the same even when the horizontal direction × vertical direction = P × Q.

FIG. 3 is a diagram showing a state after the matrix of FIG. 2 has been converted. The reference numerals in the drawing are the same as those in FIG.

As shown in FIG. 3, the pseudo halftone image for one page shown in FIG. 2 is used for each pixel at the same position in each dither matrix (the same numbers 1, 2,... In FIG. 2). , 16)
Converted into one image, a total of 16 (one of the pseudo halftone images)
Pixels, 4 × 4 = M × N) image data are created.

As a result, the converted image data shown in FIG. 3 is converted into a thinned-out image of only pixels at the same position, in other words, an image formed only from pixels having the same threshold number for determining the density level. become.

Therefore, the decimated image in FIG. 3 has an extremely high correlation as compared with the adjacent dots of the pseudo halftone image.

Next, a processing method for converting a pseudo halftone image as shown in FIG. 2 as shown in FIG. 3 will be described.

4 (1) to 4 (4) are diagrams for explaining the operation of the pseudo halftone image conversion process in the information processing apparatus of the present invention, wherein (1) is an original image, and (2) is data for 4 rasters. ,
(3) is the data obtained by rotating the data of (2) by 90 °,
(4) is a diagram showing a state of data after conversion. The reference numerals in the drawing are the same as those in FIG.

As shown in FIG. 4 (1), 2
From the digitized pseudo halftone image, its M × N (dot)
M × N images extracted in the main scanning and sub-scanning directions are generated for each element of the dither matrix, and run-length encoding is performed on the generated images.

In FIGS. 4 (1) to 4 (4), a small image is shown as a model so that the dot position at the time of conversion can be easily understood. However, even in the case of a large image such as a normal one page, FIG. The principle is exactly the same.

The pseudo halftone image has a number of “0” and “1” for M × N dots in an M × N (dot) matrix.
Is a method of expressing the density of each pixel by gradation by giving information on the number of states.

The encoding process described above with reference to FIGS. 2 to 4, that is, the encoding process by the information processing apparatus of the present invention is realized by the configuration of FIG. 1 described below.

FIG. 1 is a functional block diagram showing one embodiment of a main part configuration of an information processing apparatus having a pseudo halftone image processing function of the present invention. In the drawings, 1 is an image compression / decompression means, 2 is an image conversion means, 3 is an image input device, 4
Denotes a first image memory, 5 denotes a second image memory, and 6 denotes a code memory.

The function of each part in the block diagram of FIG. 1 is as follows.

The image compression / decompression means 1 has a function of compressing or decompressing input image data, and corresponds to the image compression / decompression controller 18 in FIG.

The image conversion means 2 is a conversion means having a function of performing image conversion, and basically corresponds to the graphics controller 17 in FIG. 7, but in the information processing apparatus of the present invention,
With respect to the pseudo halftone image of one page, the image extracted in the main scanning direction and the sub-scanning direction for each pixel at the same position of the dither matrix and thinned out by 1 / (M × N) of the original image is M × It also has an image generation function for generating N images.

The image input device 3 is an image input unit such as a scanner.
This corresponds to the image scanner 21 in FIG.

The first image memory 4 is a memory for storing image data to be edited, and a part of the area of the image memory 19 in FIG. 7 is allocated.

The second image memory 5 is a memory for storing the converted image data. Similarly, a part of the area of the image memory 19 in FIG. 7 is allocated.

The code memory 6 is a memory for storing a code obtained by encoding the original image data.
Is equivalent to

Next, the operation of the block diagram shown in FIG. 1 will be described with reference to the flowchart.

FIG. 5 is a flowchart showing a flow of processing at the time of image compression in the information processing apparatus of the present invention shown in FIG. In the drawing, # 1 to # 9 indicate steps.

In step # 1, original image data is read by the image input device 3 by the dither method.

In the next step # 2, when the image data is stored in a predetermined area in the first image memory 4, original image data as shown in FIG. 4 (1) is obtained.

In step # 3, with respect to the original image stored in the first image memory 4, the original image data of N (= 4) times the raster width is read, and image data as shown in FIG. 4 (2) is created.

In step # 4, the original image is converted by the image conversion means 2.
Rotate 90 ° and convert to data as shown in FIG. 4 (3).

In step # 5, the image data rotated 90 ° in FIG. 4 (3) is multiplied by the raster width by M, and 4 × 4 (= M × N) sheets in FIG. Create data for

In step # 6, the image data converted into the state shown in FIG. 4 (4) is stored in a predetermined area of the second image memory 5.

Proceeding to step # 7, the image data converted to the state shown in FIG. 4 (4) stored in the second image memory 5 by the image compression / decompression means 1 is read out, and the image is compressed by run-length encoding. I do.

In step # 8, the code after compression is stored in the code memory 6.

In step # 9, the run-length encoded code data stored in the code memory 6 is transferred to an optical disk (16 in FIG. 7) and stored.

By the above processing of steps # 1 to # 9, the third
As described with reference to the drawing, image data with a high speed and a high compression rate can be obtained.

In the conventional image compression method, the processing of steps # 3 to # 6 is not performed in the flow of FIG.

That is, in the information processing apparatus having the pseudo halftone image processing function of the present invention, the dots having the same number of each matrix can be easily and quickly taken in simply by changing the raster and rotating.

2 and 3, the original image is composed of 3 × 4 (= P × Q) pixels in the 4 × 4 (= M × N) matrix. This is the case.

However, one page is usually a basic matrix 4 × 4
(= M × N) is composed of P × Q pixels.

Also in this case, the converted image is P × Q (or Q ×
P) 4 × 4 (= M × N) dot images are obtained.

According to the information processing apparatus having a pseudo halftone image processing function of the present invention, from the binarized pseudo halftone image, dots in each dither matrix of M × N as a reference unit are obtained. Since an image is generated by extracting dots at the same position in the matrix (where the threshold number corresponding to the density level is the same), a clear relationship occurs between the dots.

Then, run-length encoding is performed on the dots having mutual relevance generated by such an extraction process, so that the features of run-length encoding are fully utilized.

In addition, as described in the embodiment, by changing the raster and rotating it by 90 °, high-speed conversion processing becomes possible, and the image data of the dot with the same number in each matrix is quickly stored in the same memory. Can be included.

Therefore, an excellent effect that the compression ratio of the binarized pseudo halftone image is remarkably improved and the time required for the compression processing is shortened is obtained.

[Brief description of the drawings]

FIG. 1 is a functional block diagram showing an embodiment of a main part of an information processing apparatus having a pseudo halftone image processing function according to the present invention, and FIG. 2 is a diagram showing a state of dither matrix before image conversion. FIG. 3 is a diagram showing a state after the matrix of FIG. 2 is converted. FIGS. 4 (1) to (4) are diagrams showing a pseudo halftone image conversion process in the information processing apparatus of the present invention. FIG. 5 is a flow chart showing a flow of processing at the time of image compression in the information processing apparatus of the present invention shown in FIG. 1, and FIGS. 6 (1) to (10) are Each pixel has 4 ×
FIG. 7 is a diagram showing an example of a dither pattern formed from dots 4 (dots). FIG. 7 is a functional block diagram showing an example of a main part configuration of a conventional information processing apparatus having a pseudo halftone image processing function. In the drawings, 1 is an image compression / decompression means, 2 is an image conversion means, 3 is an image input device, 4 is a first image memory, 5 is a second image memory, and 6 is a code memory.

Claims (1)

(57) [Claims] 1. An M × N pixel area comprising at least image input means for converting a halftone image into digital information by dithering or the like, display means, memory means, and a central processing unit such as a CPU. In an information processing system having an image processing function including a compression process of a binarized pseudo-halftone image by a dither method or the like using a reference unit as a reference unit, the binarized pseudo-halftone image is converted to a dither matrix reference A pixel area dividing unit that divides the pixel area into M × N pixel areas, and a first area that reads out the raster width of the pseudo halftone image data for one page of the divided M × N pixel area by N times Data reading means, and data read from the first data reading means
{Data rotating means for rotating; second data reading means for reading data rotated by the data rotating means by multiplying the raster width by M times; and one page read from the second data reading means. For each half-tone pseudo halftone image, M × N images extracted in the main scanning direction and sub-scanning direction and decimated to 1 / (M × N) of the original image for each pixel at the same position in the dither matrix Image generating means for generating, and run-length encoding means for performing run-length encoding processing on the image generated by the image generating means, wherein the pseudo halftone image binarized by the dither method or the like is In the compression process, before the run-length encoding, the original image is converted and generated into M × N images by the image generating means,
An information processing apparatus for performing run-length encoding on a generated image.