US20030193679A1
Expired / Lapsed
US
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Image processing apparatus and method
Assignee: Canon Inc
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Filing: 2003-04-10
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Granted: —
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Expires: 2023-04-10
Abstract
Abstract Disclosed are an image processing apparatus and method for the purpose of preventing overlapping of dots between two colors in low-density areas in color pseudo-grayscale processing, thereby obtaining excellent placement of the dots of each color. When a color image is binarized, an error is added to a respective one of color components (I 0 ,I 1 ), after which output decision means ( 2 ) decides an output value in accordance with the value of the sum in such a manner that the sum of pixel values after conversion will be rendered constant. Error calculation means ( 3 - 0, 3 - 1 ) calculate differences between pixel values before and after binarization as errors, and error diffusion means ( 9 - 0, 9 - 1 ) calculate values to be diffused to a neighboring pixel. Weighting coefficients used at such time are decided in accordance with combinations of values of the color components (I 0 ,I 1 ) of pixel values in the original image. The output value decided by the output decision means ( 2 ) is printed out by a printer or the like.
Inventors
- 👤 Osamu Iwasaki
- 👤 Naoji Otsuka
- 👤 Hitoshi Nishikori
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-09 09:58
CPC Classifications
H; H04; H04N; H04N1/00; H04N1/46; H04N1/52; H04N1/56; H04N1/58
Claims Analysis
Total Claims: 19
Claim 1
Independent Claim
151 words
1 . An image processing apparatus for processing multivalued color image data that includes a plurality of color components, comprising: adding unit adapted to add per-color-component quantization error values from a neighboring pixel to a respective ones of a plurality of color components included in a pixel of interest; quantization unit adapted to correlate a sum of the values of each of the color components to which the error value has been added by the adding unit to a sum of values after conversion, and deciding the value of each color component after conversion upon distributing the sum of pixel values after the conversion in accordance with the ratio of each of the color components before conversion; and coefficient decision unit adapted to decide diffusion coefficients, which diffuse quantization error to neighboring pixels, based upon the value of each of the plurality of color components included in the pixel of interest.
Claim 2
Dependent Claim
151 words
1 . An image processing apparatus for processing multivalued color image data that includes a plurality of color components, comprising: adding unit adapted to add per-color-component quantization error values from a neighboring pixel to a respective ones of a plurality of color components included in a pixel of interest; quantization unit adapted to correlate a sum of the values of each of the color components to which the error value has been added by the adding unit to a sum of values after conversion, and deciding the value of each color component after conversion upon distributing the sum of pixel values after the conversion in accordance with the ratio of each of the color components before conversion; and coefficient decision unit adapted to decide diffusion coefficients, which diffuse quantization error to neighboring pixels, based upon the value of each of the plurality of color components included in the pixel of interest.
Claim 3
Dependent Claim
45 words
2 . The apparatus according to claim 1 , wherein if the color components are approximately equal to one another, said coefficient decision unit decides the diffusion coefficients in such a manner that the same diffusion coefficients are used for each of the color components.
Claim 4
Dependent Claim
80 words
3 . The apparatus according to claim 1 , wherein if the value of each of the color components before quantization is greater than the value of each of the color components after quantization in regard to the pixel of interest, said coefficient decision unit decides the diffusion coefficients in such a manner that the smaller the difference between these values, the greater the diffusion ratio of the error value diffused to a pixel that follows the pixel of interest.
Claim 5
Dependent Claim
72 words
4 . The apparatus according to claim 1 , wherein said coefficient decision unit decides the diffusion coefficients in such a manner that the smaller the value of a certain color component before quantization in regard to the pixel of interest, the diffusion coefficients of the other color components are decided so as to increase the diffusion ratio of the error value diffused to a pixel that follows the pixel of interest.
Claim 6
Dependent Claim
153 words
5 . A program for causing multivalued color image data that includes a plurality of color components to be processed by a computer, said program causing the computer to execute as the following steps of: adding per-color-component quantization error values from a neighboring pixel to a respective ones of a plurality of color components included in a pixel of interest; correlating a sum of the values of each of the color components to which the error value has been added by said adding step to a sum of values after conversion, and deciding the value of each color component after conversion upon distributing the sum of pixel values after the conversion in accordance with the ratio of each of the color components before conversion; and deciding diffusion coefficients, which diffuse quantization error to neighboring pixels, based upon the value of each of the plurality of color components included in the pixel of interest.
Claim 7
Dependent Claim
153 words
5 . A program for causing multivalued color image data that includes a plurality of color components to be processed by a computer, said program causing the computer to execute as the following steps of: adding per-color-component quantization error values from a neighboring pixel to a respective ones of a plurality of color components included in a pixel of interest; correlating a sum of the values of each of the color components to which the error value has been added by said adding step to a sum of values after conversion, and deciding the value of each color component after conversion upon distributing the sum of pixel values after the conversion in accordance with the ratio of each of the color components before conversion; and deciding diffusion coefficients, which diffuse quantization error to neighboring pixels, based upon the value of each of the plurality of color components included in the pixel of interest.
Claim 8
Dependent Claim
44 words
6 . The program according to claim 5 , wherein if the color components are approximately equal to one another, said deciding step decides the diffusion coefficients in such a manner that the same diffusion coefficients are used for each of the color components.
Claim 9
Dependent Claim
79 words
7 . The program according to claim 5 , wherein if the value of each of the color components before quantization is greater than the value of each of the color components after quantization in regard to the pixel of interest, said deciding step decides the diffusion coefficients in such a manner that the smaller the difference between these values, the greater the diffusion ratio of the error value diffused to a pixel that follows the pixel of interest.
Claim 10
Dependent Claim
71 words
8 . The program according to claim 5 , wherein said deciding step decides the diffusion coefficients in such a manner that the smaller the value of a certain color component before quantization in regard to the pixel of interest, the diffusion coefficients of the other color components are decided so as to increase the diffusion ratio of the error value diffused to a pixel that follows the pixel of interest.
Claim 11
Dependent Claim
151 words
9 . An image processing method for processing multivalued color image data that includes a plurality of color components, comprising: an adding step of adding per-color-component quantization error values from a neighboring pixel to a respective ones of a plurality of color components included in a pixel of interest; a quantization step of correlating a sum of the values of each of the color components to which the error value has been added by the adding step to a sum of values after conversion, and deciding the value of each color component after conversion upon distributing the sum of pixel values after the conversion in accordance with the ratio of each of the color components before conversion; and a coefficient decision step of deciding diffusion coefficients, which diffuse quantization error to neighboring pixels, based upon the value of each of the plurality of color components included in the pixel of interest.
Claim 12
Dependent Claim
151 words
9 . An image processing method for processing multivalued color image data that includes a plurality of color components, comprising: an adding step of adding per-color-component quantization error values from a neighboring pixel to a respective ones of a plurality of color components included in a pixel of interest; a quantization step of correlating a sum of the values of each of the color components to which the error value has been added by the adding step to a sum of values after conversion, and deciding the value of each color component after conversion upon distributing the sum of pixel values after the conversion in accordance with the ratio of each of the color components before conversion; and a coefficient decision step of deciding diffusion coefficients, which diffuse quantization error to neighboring pixels, based upon the value of each of the plurality of color components included in the pixel of interest.
Claim 13
Dependent Claim
45 words
10 . The method according to claim 9 , wherein if the color components are approximately equal to one another, said coefficient decision step decides the diffusion coefficients in such a manner that the same diffusion coefficients are used for each of the color components.
Claim 14
Dependent Claim
80 words
11 . The method according to claim 9 , wherein if the value of each of the color components before quantization is greater than the value of each of the color components after quantization in regard to the pixel of interest, said coefficient decision step decides the diffusion coefficients in such a manner that the smaller the difference between these values, the greater the diffusion ratio of the error value diffused to a pixel that follows the pixel of interest.
Claim 15
Dependent Claim
72 words
12 . The method according to claim 9 , wherein said coefficient decision step decides the diffusion coefficients in such a manner that the smaller the value of a certain color component before quantization in regard to the pixel of interest, the diffusion coefficients of the other color components are decided so as to increase the diffusion ratio of the error value diffused to a pixel that follows the pixel of interest.
Claim 16
Dependent Claim
18 words
13 . A computer-readable recording medium on which the program set forth in claim 5 has been recorded.
Claim 17
Dependent Claim
149 words
14 . An image processing apparatus comprising: adding unit, to which a multivalued image signal of two or more colors is input, for adding, on a per-color basis, error signals from a pixel that has already undergone pseudo-grayscale processing to respective one of the colors; output decision unit, to which outputs from each of said adding unit are input, for deciding a pseudo-grayscale output for every color; error calculation unit for each color for calculating an error at a pixel of interest based upon an output for every color from said output decision unit and outputs from said adding unit for every color; error diffusion unit for diffusing the error for every color to neighboring pixels; and weighted-error diffusion decision unit, to which the multivalued image signal of two or more colors is input, for deciding, on a per-color basis, an error diffusion allocation in said error diffusion unit.
Claim 18
Dependent Claim
149 words
14 . An image processing apparatus comprising: adding unit, to which a multivalued image signal of two or more colors is input, for adding, on a per-color basis, error signals from a pixel that has already undergone pseudo-grayscale processing to respective one of the colors; output decision unit, to which outputs from each of said adding unit are input, for deciding a pseudo-grayscale output for every color; error calculation unit for each color for calculating an error at a pixel of interest based upon an output for every color from said output decision unit and outputs from said adding unit for every color; error diffusion unit for diffusing the error for every color to neighboring pixels; and weighted-error diffusion decision unit, to which the multivalued image signal of two or more colors is input, for deciding, on a per-color basis, an error diffusion allocation in said error diffusion unit.
Claim 19
Dependent Claim
34 words
15 . A color printer comprising: the image processing apparatus set forth in claim 1; and a printer engine for printing multivalued color image data that has been quantized by said image processing apparatus.
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