Image processing method, image processing apparatus and image forming apparatus

An image processing device and image processing technology, applied in the direction of image communication, electrical components, etc., can solve the problems of texture and other problems, and achieve the effect of improving texture, reducing the number of tones, and maintaining good

Inactive Publication Date: 2005-12-28
SHARP KK
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  • Abstract
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Problems solved by technology

[0009] However, in the dithering method, the dithering matrix of the same pattern is used for binarization, so there is a problem that a texture (texture) unique to dithering, that is, a periodic pattern image is generated in the binarized image.
[0010] On the other hand, in the error diffusion method, since the error is diffused according to the same matrix for each pixel, the quantization error in the highlight part with a large tone value is diffused in a chain, and there is a problem of correlation between pixels.
Specifically, since pixels with differ

Method used

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  • Image processing method, image processing apparatus and image forming apparatus
  • Image processing method, image processing apparatus and image forming apparatus
  • Image processing method, image processing apparatus and image forming apparatus

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Embodiment approach 1

[0089] 3 is a block diagram showing a configuration example of an image processing device according to Embodiment 1 of the present invention. The image processing device is a device that generates and outputs image data Po(X, Y) in which the number of tones of image data Pi(X, Y) input to the image processing device is reduced. For example, the image processing device generates and outputs image data Po(X, Y) that quantizes image data Pi(X, Y) of 256 tones and reduces to, for example, 4 tones. Here, the image data Pi(X, Y) is the tone value of an image composed of pixels arranged in a two-dimensional matrix in X and Y directions perpendicular to each other, that is, horizontal rows and vertical rows. X represents the position on the horizontal line of the image, and Y represents the position on the vertical line of the image.

[0090] The image processing device includes an image data storage unit 11 for temporarily storing input image data Pi(X, Y). The image data Pi(X, Y) ...

Embodiment approach 2

[0130] 9 is a block diagram showing a configuration example of an image processing device according to Embodiment 2 of the present invention. The image processing apparatus of Embodiment 2 is the same as the image processing apparatus of Embodiment 1 shown in FIG. In addition to the addition unit 15 , the frequency inverse conversion unit 16 , and the threshold value processing unit 17 , a DC component determination unit 18 is also included. The configuration, function, and effect of the image processing device of Embodiment 2 other than the DC component determination unit 18 are the same as those of the image processing device of Embodiment 1, so the same reference numerals are assigned to the same components. and omit their detailed descriptions.

[0131] The DCT coefficient Qj(S, T) output from the frequency conversion unit 12 is input to the DC component determination unit 18 included in the image processing device according to the second embodiment. The DC component det...

Embodiment approach 3

[0136] 10 is a block diagram showing a configuration example of an image processing apparatus according to Embodiment 3 of the present invention. The image processing apparatus of Embodiment 3 is the same as the image processing apparatus of Embodiment 2 shown in FIG. In addition to the addition unit 15 , frequency inverse conversion unit 16 , threshold value processing unit 17 , and DC component determination unit 18 , it also includes a LUT (Look Up Table) unit 19 that stores DCT coefficients of blue noise used for noise addition. Furthermore, the LUT unit 19 is connected to the noise addition unit 15 . The structure, function, and effect of the image processing device of Embodiment 3 other than the LUT unit 19 are the same as those of the image processing device of Embodiment 2, so the same reference numerals are assigned to the same components and omitted. their detailed description.

[0137] The LUT unit 19 performs discrete cosine transform on the image data having blu...

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Abstract

An image processing method is provided, which converts image data into image data having spatial frequency components, judges whether the absolute value of the coefficient of a predetermined frequency component of the transformed image data is greater than or equal to a predetermined value, and changes the exchange of the image data according to the judgment result. The coefficients of the components are used to inverse transform the image data with the changed coefficients into image data having spatial coordinate components, compare the tone value of the inversely transformed image data with a predetermined value, and convert it into a tone value corresponding to the comparison result. By performing appropriate image processing according to the characteristics of the image, the characteristic portion of the original image can be kept well, and the number of tones of the image can be reduced.

Description

technical field [0001] The present invention relates to an image processing method for performing image processing by changing the spatial frequency components of image data, an image processing device for executing the image processing method, and an image forming device equipped with the image processing device. Background technique [0002] As a method of reducing the number of tones of an image including halftones, for example, as a method of binarizing an image with 256 tones into a two-tone image, it is known to perform binarization by comparing the tonal value of the image with a predetermined value, that is, a threshold value. method, dithering method, and error diffusion method, etc. (Japanese Patent Application Laid-Opens No.2000-299783, Japanese Patent Application Laid-Opens No.2000-299783, No.H06 -189119(1994) and No.2002-10085). [0003] FIG. 1 is a schematic diagram showing an example of a 4×4 dither matrix used when binarizing a 16-tone image in a conventiona...

Claims

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Application Information

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IPC IPC(8): H04N1/405
Inventor 加藤木央光
Owner SHARP KK
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