JPH0896119A - Image processor - Google Patents

Abstract

PURPOSE: To suppress the generation of texture when an image is reduced by thinning out. CONSTITUTION: Image data which are divided into blocks are inputted to a pattern matching device 42104. This pattern matching device 42104 calculates to the inputted image blocks on the basis of featured image blocks of an image such as a line drawing, a contour, a dither image, and an error diffusion image and outputs which feature is expressed most, as a label in a feature table. On the basis of the discriminated information, a thinning-out device 42107 thins out the image by the best thinning-out method among plural thinning-out methods.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image processing apparatus such as a computer display or a printer for reducing an image by thinning and outputting the image.

[0002]

2. Description of the Related Art Conventionally, a thinning device in an apparatus for outputting image information has a structure as shown in FIG. 5, for example. That is, in FIG. 5, reference numeral 42401 is an input buffer memory, 42402 is a horizontal counter that determines the horizontal thinning rate, 42403 is a vertical counter that determines the vertical thinning rate, and 42404 is the pixel adjacent to the thinned pixel. OR device that takes the logical sum of
42405 is an address controller that manages the information in the input buffer memory 42401.

In the conventional thinning device having the above structure,
When the image information is input, once the input buffer memory 4
Information is stored in 2401. Since the capacity of the input buffer memory 42401 is thinned out in the vertical direction,
At least one line is required.

FIG. 6 is a schematic diagram showing the thinning operation. That is, when the image information is input to the device shown in FIG. 5, the horizontal counter 42402 counts the number of pixels in the horizontal direction, and the horizontal counter 42402 corresponds to a predetermined thinning rate.
402 outputs a carry signal. This carry signal is output, for example, when one pixel is thinned out of five pixels, that is, when 20% reduction is performed, a thinned pixel is input every five pixels.

The thinned pixel is not output but is logically ORed with the pixel to be input next, and the result is used as the next pixel. In this way, for example, horizontal reduction processing as shown in FIG. 6B is performed, and image information is output at any time.

Next, the processing for thinning out in the vertical direction will be described.

In addition to the horizontal counter 42402 which counts in the horizontal direction when image information is input, a vertical counter 42403 which counts each time image information for one line is received is provided by a vertical thinning rate. To decide. The lines to be thinned out are accumulated in the input buffer memory 42401 for each line, the logical sum is obtained with the image information of the next one line, and the result of the logical sum is set as the line next to the thinning line ( FIG. 6A).

Since the thinning process is performed in this manner,
Even if the image information is thinned, the thin lines can be thinned out ((c) in FIG. 6).

[0009]

However, in the above-described conventional thinning-out device, when an image subjected to dithering is thinned out in the image reducing method, a texture is generated depending on the thinning cycle, and the quality of the output image is reduced. May be greatly impaired.

Further, in the above-described conventional thinning-out method, since consideration is not given to the color information of the image, thinning-out
There is a problem that the reproduced image after interpolation has poor color reproducibility.

The present invention has been made in view of the above problems, and an object thereof is to provide an image processing apparatus capable of suppressing the occurrence of texture when an image is reduced by thinning.

Another object of the present invention is to provide an image processing apparatus which maintains the reproducibility of the color of an image even if it is reduced.

[0013]

[Means for Solving the Problems] and

In order to achieve the above-mentioned object, the invention according to claim 1 is an image processing apparatus for reducing an input binary image and outputting the same, and a means for judging characteristics of the binary image, A lookup table that stores a plurality of decimation methods corresponding to image features; and a selection unit that selects a decimation method for performing the reduction from the plurality of decimation methods based on the binary image features. And the reduction is performed by the selected thinning method.

In the above configuration, it functions to suppress the generation of texture when the image is reduced by thinning.

According to the invention described in claim 5, further, regarding the binary image divided into the plurality of regions,
The image forming apparatus includes a unit that calculates the density of each region, and a converting unit that performs a predetermined density conversion on the reduced image according to the calculated density.

With this configuration, it functions to maintain the reproducibility of the color of the image even after the reduction.

[0017]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of the present invention will be described in detail below with reference to the accompanying drawings. <First Embodiment> A first embodiment of the present invention will be described below.

FIG. 1 is a block diagram showing the structure of a thinning device according to the first embodiment of the present invention. In the figure,
Reference numeral 42101 is an input buffer, 42102 is a first address controller, 42103 is a block divider, 4
2103 is a block divider, 42104 is a pattern matching device, 42105 is a lookup table, 42
106 is a pattern table, 42107 is a thinning device,
42108 is an output buffer and 42109 is a second
Address controller.

FIG. 2 is a diagram showing the input order of the image data used in this embodiment. Here, the image data is input in the raster order. That is, scanning is performed from the upper left pixel in the effective pixel area toward the right, and the pixel data string is received until the scan reaches the lower right.

The input image data is first stored in the input buffer 42101. Address controller 4
2102 outputs an address to the input buffer 42101 so that the input pixel data is accumulated in raster order, and outputs it to the block divider 42103 in the subsequent stage so as to form a predetermined block as follows. To be done.

That is, in the example shown in FIG. 2, one column of the input image consists of 64 pixels, and as is apparent from the figure, the first 4 × 4 block is become that way.

Therefore, the required capacity of the input buffer 42101 in this embodiment is the block divider 42 in the subsequent stage.
(Number of pixels in one row) of the block divided by 103 x (1
The number of pixels in a column).

The image data in blocks as described above is input to the pattern matching device 42104.
This pattern matching device 42104 is stored in a pattern table 42106, as shown in FIG.
Based on the characteristic image blocks of images such as line drawings, contours, dither images, and error diffusion images, the correlation is calculated for the input image blocks, and which feature is best represented in the feature table. Output as the label.

Then, based on the identified information, the thinning-out device 42107 thins out the image from the plurality of thinning-out methods by a more optimal thinning-out method. For example, thin lines are left in the image block identified as a line drawing, and black is thinned out in the case of a black thin line and white is left in the case of a white thin line. Further, if the image block is identified as a dither image, it is thinned out so as to preserve the white / black ratio.

The image information thinned out in this way is
The output order is temporarily stored in the output buffer 42108, the output order is changed to the order shown in the block of FIG. 2, and the thinned images are output.

As described above, according to this embodiment,
The features of the input image are identified for each predetermined image block, and the image is thinned by applying the optimal thinning method for each feature amount, which suppresses the occurrence of texture when the image is reduced and is visually superior. A reduced image can be obtained. <Second Embodiment> A second embodiment according to the present invention will be described below.

FIG. 4 is a block diagram showing the arrangement of an image thinning apparatus according to this embodiment. In the figure, Y
Since the internal circuits corresponding to the respective colors of (yellow), M (magenta), C (cyan), and K (black) have the same configuration, only the circuit configuration corresponding to Y is shown.

In FIG. 4, reference numeral 40101 is a color separation device for separating the input image into Y, M, C and K colors, and 40.
Reference numeral 102 is an input buffer memory, 40103 is a blocking device for extracting a 4 × 4 matrix from image information,
40104 is a counter for calculating the number of effective dots in a block, 40105 is a matrix table for storing a dither matrix corresponding to the count number, 401
Reference numeral 06 denotes an error counter that counts the error that occurs when the image is reduced, and 40107 denotes the matrix table 40.
A dithering device for converting into a 3 × 3 dither matrix based on the information from 105, and 40108 is an output buffer.

The operation of the image thinning apparatus according to this embodiment having the above structure will be described.

In the device according to the present embodiment, the color separation device 40101 separates the image data into Y, M, and C colors, and K is added to obtain a visually good output. Output as four colors of Y, M, C and K. Since the reduction operation is performed independently for the four colors, Y will be described here.

The respective colors separated by the color separation device 40101 are input to the buffer memory 40102. In the buffer memory 40102, image data is line by line, and lines required by the blocker 40103 in the subsequent stage are input. Accumulates until the number is reached. It should be noted that the buffer memory 40102 corresponds to the block size (the number of lines) ×
The size (horizontal size of image) is required. For example,
When cutting out a block of 4 pixels × 4 pixels, since 4 pixels are required in the vertical direction, a buffer memory for 4 lines is required.

When the image data is recorded in a predetermined buffer memory, the matrix extracting device 40103 then specifies an address for reading the data in block units. The address to be given at this time is x, x + 1, x + 2, x + 3 x + n, X + n + 1, X + n + 2, X + n + 3 x + 2n, X + 2n + 1, X + 2n + 2, X + 2n + 3 x + 3n, X + 3n + 1, where n is the horizontal pixel of the image and x is the cutout start address. A 4 × 4 block can be cut out from X + 3n + 3. After cutting out in this way, the counter 40104 calculates the existence rate of each color in the block.

In this embodiment, the counter value is increased / decreased by the input from the outside to enable fine adjustment of delicately different colors.

The matrix table 40105 is provided with a 3 × 3 matrix table corresponding to the number of counts, and the output from this is passed to the 3 × 3 dithering device 40107 to synthesize the respective colors. After that, the reduced image is output through the output buffer 40108. In addition,
In this embodiment, since the 4 × 4 block is converted into the 3 × 3 block, the reduction of 75% is performed.

In the matrix table 40105, 1
Mapping from 6 gradations to 9 gradations is performed. The error generated during this mapping is accumulated in the error counter 40106 and passed to the block to be processed next. And
The above-mentioned mapping is performed, and the block in which the gradation is obtained is converted into a 3 × 3 pixel dither matrix and output.

As described above, according to this embodiment,
When reducing and converting an image from a 4 × 4 block to a 3 × 3 block, the density in the block is converted, so that there is little change in the color mixture ratio after reduction and excellent reduction in color is performed. be able to.

The present invention may be applied to a system composed of a plurality of devices or an apparatus composed of 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.

[0038]

As described above, according to the present invention,
By selecting the thinning method according to the characteristics of the image, it is possible to suppress the occurrence of texture at the time of reducing the image and provide a visually excellent reduced image.

According to another aspect of the invention, the reproducibility of the color of the reduced image can be maintained by subjecting the reduced image to a predetermined density conversion.

[0040]

[Brief description of drawings]

FIG. 1 is a block diagram showing a schematic configuration of a thinning device according to a first embodiment of the present invention.

FIG. 2 is a diagram showing an input order of image data used in the first embodiment.

FIG. 3 is a diagram showing patterns stored in a pattern table according to the first embodiment.

FIG. 4 is a block diagram showing a configuration of an image thinning apparatus according to a second embodiment.

FIG. 5 is a block diagram showing a schematic configuration of a conventional thinning device.

FIG. 6 is a diagram illustrating a conventional thinning method.

[Explanation of symbols]

42101 Input buffer 42102, 42109, 42405 Address controller 42103 Block division device 42104 Pattern matching device 42105 Lookup table 42106 Pattern table 42107 Decimation device 42108 Output buffer 42401 Input buffer memory 42402 Horizontal counter 42403 Vertical counter 42404 OR device

 ─────────────────────────────────────────────────── (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 (7)

[Claims] 1. An image processing apparatus for reducing an input binary image and outputting the reduced binary image, a means for determining a characteristic of the binary image, and a lookup for storing a plurality of thinning methods corresponding to the characteristic of the image in advance. A table and selection means for selecting a decimation method for performing the reduction from the plurality of decimation methods based on the characteristics of the binary image, and performing the reduction by the selected decimation method. An image processing device characterized by: 2. The selecting means is a designated reduction ratio or 2
The image processing apparatus according to claim 1, wherein the thinning method is selected based on the binarization method. 3. The selecting means further comprises means for dividing the input binary image into a plurality of predetermined regions, and analysis for analyzing a predetermined structure of the binary image divided into the plurality of regions. The image processing apparatus according to claim 1, further comprising means for selecting a thinning method using the information obtained by the analysis as a characteristic of the binary image. 4. The analysis unit analyzes the predetermined structure based on the correlation between the feature of the image and the binary image divided into the plurality of regions. The image processing device described. 5. Further, the two divided into the plurality of areas.
4. The value image according to claim 3, further comprising: a unit that calculates a density of each area; and a conversion unit that performs a predetermined density conversion on the reduced image according to the calculated density. Image processing device. 6. The converting means further comprises means for calculating an error between the input binary image and the reduced image, and means for adding the error to an adjacent region. The image processing apparatus according to claim 5. 7. The error includes Y (yellow), M (magenta), C (cyan), and K that form an image in the area.
The image processing apparatus according to claim 6, wherein the image processing apparatus is calculated based on a color presence rate of each color of (black).