Color difference judgment apparatus and method
First Claim
1. A system for judging a color difference between a first color and a second color in RGB color space, comprising:
- a first calculator, arranged to calculate distance between the first and second colors in the RGB color space;
a storage, arranged to store a plurality of threshold values which respectively correspond to divisional spaces composing the RGB color space;
a selector, arranged to select a threshold value from the plurality of threshold values stored in said storage, wherein the threshold value to be selected corresponds to the divisional space containing one of the first and second colors;
a decider, arranged to compare the distance calculated by said first calculator and the threshold value selected by said selector, and to decide that the color difference between the first and second colors lies within an allowable range if the distance is equal to or less than the threshold value; and
a second calculator, arranged to calculate the threshold value to be stored in said storage by the following steps;
converting a voluntary color contained in the divisional space into a first value in a uniform color space;
computing a plurality of second values spaced away by an allowable maximum value of the color difference from the first value in the uniform color space;
converting the plurality of second values into plural colors in the RGB color space;
computing an average distance between the voluntary color and the converted plural colors in the RGB color space;
obtaining average distances for a plurality of voluntary colors contained in the divisional space by repeatedly executing the converting steps and the computing steps; and
averaging the average distances to calculate the threshold value corresponding to the divisional space which contains the plurality of voluntary colors.
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Abstract
The present invention is related to a color difference judgment apparatus for judging a color difference between a first color and a second color in RGB color space. The method is comprising: distance calculating means for calculating distance between the first and second colors in RGB color space; threshold-value candidate storage means for storing a plurality of threshold-value candidates; threshold-value selecting means for selecting a threshold value from among the plurality of threshold-value candidates that have been stored in the threshold-value candidate storage means; and comparing decision means for comparing the distance calculated by the distance calculating means and the threshold value selected by the threshold-value selecting means and deciding that the color difference between the first and second colors lies within an allowable range if the distance is less than the threshold value.
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Citations
10 Claims
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1. A system for judging a color difference between a first color and a second color in RGB color space, comprising:
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a first calculator, arranged to calculate distance between the first and second colors in the RGB color space; a storage, arranged to store a plurality of threshold values which respectively correspond to divisional spaces composing the RGB color space; a selector, arranged to select a threshold value from the plurality of threshold values stored in said storage, wherein the threshold value to be selected corresponds to the divisional space containing one of the first and second colors; a decider, arranged to compare the distance calculated by said first calculator and the threshold value selected by said selector, and to decide that the color difference between the first and second colors lies within an allowable range if the distance is equal to or less than the threshold value; and a second calculator, arranged to calculate the threshold value to be stored in said storage by the following steps; converting a voluntary color contained in the divisional space into a first value in a uniform color space; computing a plurality of second values spaced away by an allowable maximum value of the color difference from the first value in the uniform color space; converting the plurality of second values into plural colors in the RGB color space; computing an average distance between the voluntary color and the converted plural colors in the RGB color space; obtaining average distances for a plurality of voluntary colors contained in the divisional space by repeatedly executing the converting steps and the computing steps; and averaging the average distances to calculate the threshold value corresponding to the divisional space which contains the plurality of voluntary colors. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 10)
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9. A method for judging a color difference between a first color and a second color in RGB color space, comprising the steps of:
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calculating distance between the first and second colors in the RGB color space; selecting a threshold value from a plurality of threshold values stored in a storage, wherein each threshold value corresponds to a divisional space divided from the RGB color space, and the threshold value to be selected corresponds to the divisional space containing one of the first and second colors; comparing the calculated distance and the threshold value selected; deciding that the color difference between the first and second colors lies within an allowable range if the distance is equal to or less than the threshold value; and calculating the threshold value to be stored in the storage by the following steps; converting a voluntary color contained in the divisional space into a first value in a uniform color space; computing a plurality of second values spaced away by an allowable maximum value of the color difference from the first value in the uniform color space; converting the plurality of second values into plural colors in the RGB color space; computing an average distance between the voluntary color and the converted plural colors in the RGB color space; obtaining average distances for a plurality of voluntary colors contained in the divisional space by repeatedly executing the converting steps and the computing steps; and averaging the average distances to calculate the threshold value corresponding to the divisional space which contains the plurality of voluntary colors.
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Specification