JPH08153190A - Method and device for image processing - Google Patents

Abstract

PURPOSE: To suppress the generation of texture and provide a visually superior reduced image by thinning out image information which is divided by a dividing means according to a stored submatrix. CONSTITUTION: Image data which is inputted is stored in an input buffer 1. When the data is stored in the input buffer 1 by the number of dots of one side of the matrix of an image to be reduced X the number of dots in one column, a block dividing device 2 divides the image information outputted from the input buffer 1 into a matrix of 8×8 blocks and outputs it to a dither device 4. The divided data are sent to a counter 3 as well and the counter 3 counts effective dots in the blocks, so that its counted value is the density in the block. On the basis of gradations obtained by the dither device 4, the image data is converted into a dither matrix of 8×8 this time. Then, a thinning- out submatrix determination device 5 selects a submatrix to be thinned out horizontally.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image processing method and apparatus for reducing and outputting a pseudo multi-valued image, and more particularly to an image processing method and apparatus suitable for a device for outputting image information such as a computer display and a printer. Is.

[0002]

2. Description of the Related Art FIG. 5 is a block diagram showing a configuration of an image processing apparatus for performing a conventional thinning process. In FIG. 5, 5
Reference numeral 01 is an input buffer memory, 052 is a horizontal counter that determines the horizontal thinning rate, 503 is a vertical counter that determines the vertical thinning rate, 504 is an OR circuit that takes the logical sum of adjacent pixels of thinned pixels, and 505 is An address controller that manages information in the memory. The memory capacity of the input buffer memory 501 needs to be at least one line for thinning in the vertical direction.

In the conventional apparatus of this type, first, when image information is input, the input buffer memory 501 is temporarily input.
Store information in. When the image information is input, the horizontal counter 502 counts the number of horizontal pixels of the image information to be processed. Then, the horizontal counter 502 outputs a carry signal according to the thinning rate. The carry signal output is output, for example, when one pixel out of five pixels is thinned out, that is, when a pixel to be thinned out every five pixels is input when reducing by 20%. When this carry signal is output, the address controller controls the memory address so as not to output the pixels to be thinned out, and the OR circuit 50
4 takes the logical sum of the pixel input next and outputs it as the next pixel. In this way, horizontal reduction processing is performed, and image information is output as needed. An image before horizontal thinning is shown in FIG. 5A, and an example of the image subjected to the horizontal thinning processing is shown in FIG. 5B.

Next, the process of thinning out in the vertical direction will be described. In addition to the horizontal counter 502 when the image information is input, a vertical counter 503 that counts each time image information for one line is received determines the thinning rate in the vertical direction. The lines to be thinned out are accumulated in the input buffer memory 501 line by line, and the logical sum is obtained with the pixel information of the next one line, and the result of the logical sum is set as the line next to the thinning line. FIG. 5C shows an example of a thinned image for which the thinning processing in the vertical direction has been completed.

Since thinning is performed in this manner, thinning can be performed without thin lines disappearing even if image information is thinned.

[0006]

However, the above-mentioned conventional example has the following problems. That is, in the conventional image thinning method, when the image subjected to the dithering process is thinned out, the density of the reduced image is changed or a characteristic texture is generated depending on the thinning cycle, resulting in a large output image quality. May be damaged.

[0007]

SUMMARY OF THE INVENTION The present invention is intended to solve the above problems, and has the following structure as one means for solving the above problems. That is, it is an image processing apparatus for reducing and outputting a pseudo multi-valued image, and a first storage means for storing input image information and image information from the first storage means from a plurality of sub-matrices. Dividing means for dividing by the constituted dither matrix unit,
A second storage unit for storing the sub-matrix to be thinned out; and a thinning-out unit for thinning out the image information divided by the dividing unit according to the sub-matrix stored in the second storage unit. To do.

[0008]

With the above structure, even in the process of reducing the pseudo multi-valued image using the input image information, for example, the dither matrix, it is possible to suppress the occurrence of texture and provide a visually excellent reduced image.

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment according to the present invention will be described in detail below with reference to the drawings. FIG. 1 is a block diagram showing a configuration example of an image processing apparatus according to an embodiment of the present invention. In FIG. 1, 1 is an input buffer memory and 2 is an input image memory.
A block dividing device for dividing into × 8 blocks, 3 a counter for calculating the number of effective dots in the blocks divided by the block dividing device 2, 4 a dithering device for dithering a multi-valued image, 5 a The thinning submatrix determining device determines the thinning submatrix to be thinned by the device of this embodiment, and has a table structure. A thinning device 6 performs thinning processing on the dithered image from the dithering device 4 according to the thinning sub-matrix determined by the thinning sub-matrix determining device 5.

Next, the image reduction operation in this embodiment having the above-mentioned structure will be described. Now, in the above configuration, first, the input image data is stored in the input buffer 1. When the number of dots on one side of the matrix of the image to be reduced is stored in the input buffer 1 by the number of dots in one column, the block dividing device 2 outputs the matrix of 8 × 8 blocks from the input buffer 1. The divided image information is divided and output to the dithering device 4.

The divided data is also sent to the counter 3, and the counter 3 counts the number of effective dots in the block, and the count value becomes the density in the block. In this embodiment, the block division device 2 is 8 ×
Since the image data is divided into 8 blocks, image data of 64 gradations can be obtained. Next, the dithering device 4 converts this image data into an 8 × 8 dither matrix based on the obtained gradation. The dither matrix by the dither device 4 of this embodiment has a matrix size of 8 ×, as shown in FIG.
8, the size of the sub-matrix is 2 × 2.

A method of determining the density in the dither matrix having such a structure in this embodiment will be described below. As shown in FIG. 2, in this embodiment, the dither matrix is composed of 2 × 2 sub-matrices numbered 1 to 16, and the sub-matrices are numbered 1 to 4. To simplify the description from now on, the specification method of (dither matrix)-(sub matrix) is used to represent the pixels in the matrix. For example, 1-1 refers to the upper left pixel in the matrix, and 11-3 refers to the upper right pixel in the matrix.

When the density is "1", pixels 1-1 are filled, then pixels 2-1 and 3-1 are filled in this order. Pixels are filled. In this way, 64 gradations up to 16-4 are expressed. Next, FIG. 3 shows how images are thinned out in sub-matrix units in this embodiment. First, the input image is divided by the block dividing device 2 into an 8 × 8 dither matrix. Next, the sub-matrix determining device 5 selects a sub-matrix to be thinned out in the horizontal direction. For example, as shown in FIG. 3A, 4, 8, 11, and 15 sub-matrices are determined as thinned-out sub-matrices.
Any sub-matrix may be thinned out, but by making the ranks in the sub-matrix uniform, it is possible to minimize the change in density. The matrix thinned out in the horizontal direction is shown in FIG.

Submatrixes 1, 5 and 10 which are thinned out in the vertical direction are selected next to the matrix thinned out in the horizontal direction, for example, as shown in FIG. The matrix after the reduction process, which is thinned out in the vertical direction, is shown in (C). In this way, 75% reduction is performed, and a 6 × 6 matrix is output as the reduction result.

The operation described above is executed for the entire range of the input image, and the reduced image of this embodiment is completed. As described above, according to the present embodiment, it is possible to provide a visually excellent reduced image with a reduction method for a pseudo multi-valued image using a dither matrix, which suppresses the occurrence of texture particularly when reduced. it can.

In the above description, an 8 × 8 matrix is used as an example of the dither matrix, but the present invention is not limited to the above example.
It can be applied to matrices of any size. Further, the sub-matrix is not limited to 2 × 2, and its size is arbitrary. The present invention may be applied to a system including a plurality of devices or an apparatus including a single device. Further, it goes without saying that the present invention can be applied to the case where it is achieved by supplying a program to a system or an apparatus.

[0017]

As described above, according to the present invention, even in the process of reducing the pseudo multi-valued image using the dither matrix as the input image information, the generation of the texture is suppressed and the visually reduced image is reduced. Can be provided.

[Brief description of drawings]

FIG. 1 is a block diagram showing the configuration of an image processing apparatus according to an embodiment of the present invention.

FIG. 2 is a diagram showing an example of a format of a dither matrix used in the processing of this embodiment.

FIG. 3 is a diagram for explaining reduction processing for performing thinning processing in sub-matrix units in the present embodiment.

FIG. 4 is a schematic configuration diagram of a thinning device according to a conventional example.

FIG. 5 is a diagram showing an example of a thinning method according to a conventional example.

[Explanation of symbols]

 1 Input Buffer Memory 2 Blocking Device 3 Counter 4 8 × 8 Dithering Device 5 Decimation Device for Deciding Submatrix 6 Decimation Device 501 Input Buffer Memory 502 Horizontal Counter 503 Vertical Counter 504 OR Circuit 505 Address Controller

 ─────────────────────────────────────────────────── (72) Inventor Masafumi Matsumoto 3-30-2 Shimomaruko, Ota-ku, Tokyo Canon Inc. (72) Inventor Yuji Akiyama 3-30-2 Shimomaruko, Ota-ku, Tokyo Canon Within the corporation

Claims (8)

[Claims] 1. An image processing method in an image processing apparatus for reducing and outputting a pseudo multi-valued image, wherein input image information is temporarily stored and then the stored image information is composed of a plurality of sub-matrices. An image processing method, characterized by dividing in a matrix unit and thinning out the dither matrix image in a sub-matrix unit according to an image reduction rate. 2. The image processing method according to claim 1, wherein the dither matrix is 8 × 8. 3. The image processing method according to claim 1, wherein the sub-matrix is 2 × 2. 4. The thinning by a sub-matrix of the dither matrix is characterized by first determining a sub-matrix to be thinned out in the horizontal direction and thinning out in the horizontal direction, and then determining a sub-matrix to be thinned out in the vertical direction and thinning out in the vertical direction. The image processing method according to claim 3. 5. An image processing apparatus for reducing and outputting a pseudo multi-valued image, comprising: a first storage unit for storing input image information; and a plurality of image information from the first storage unit. Dividing means for dividing by a dither matrix unit composed of sub-matrices, second storage means for storing the thinned-out sub-matrix, and the dividing means according to the sub-matrix stored in the second storage means. An image processing apparatus comprising: a thinning-out means for thinning out the divided image information. 6. The image processing apparatus according to claim 5, wherein the dividing unit divides the image information into an 8 × 8 dither matrix. 7. The image processing apparatus according to claim 5, wherein the sub-matrix is 2 × 2. 8. The thinning by the sub-matrix of the dither matrix by the thinning means is to first determine a sub-matrix to be thinned out in the horizontal direction and then thin out in the horizontal direction, and then to determine a sub-matrix to be thinned out in the vertical direction to thin out in the vertical direction. The image processing apparatus according to any one of claims 5 to 7, characterized in that: