Patent ID: 7447350

Claim:
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.