Patent ID: 7436543

Claim:
A method of creating color conversion information for converting input color image data represented by a first color system to second color image data represented by a reproduction color system, the reproduction color system being a color system for reproducing color on a print medium using an ink set including a plurality of chromatic primary color inks that used in combination can reproduce achromatic color, the plurality of chromatic primary color inks having unequal balance of ink quantities when achromatic color is reproduced, the method comprising: (a) establishing a first correspondence relationship for converting a first tone value set represented by the first color system to a model color tone value set represented by a model color system, the model color system being a hypothetical color system of a plurality of hypothetical chromatic primary color inks, the plurality of hypothetical chromatic primary color inks having a different balance of ink quantities from the unequal balance of the plurality of chromatic primary color inks when achromatic color is reproduced; (b) establishing a color separation correspondence relationship for converting a model tone value set for each of a plurality of input colors within the model color system into a combination of ink quantities of the ink set; and (c) generating, based on the first correspondence relationship and the color separation correspondence relationship, a correspondence relationship between a first tone value set represented by the first color system and a combination of ink quantities of the ink set, and storing the generated correspondence relationship in the color conversion information, wherein a color space for ink quantities of the plurality of chromatic primary color inks is termed a primary color space, and wherein the step (b) includes: (b1) establishing a primary coloring factor for each of the plurality of chromatic primary color inks, the primary coloring factor being correlated to a primary color mixture ratio which is a ratio of ink quantities when achromatic color is reproduced by a mixture of the plurality of chromatic primary color inks; and (b2) determining a combination of ink quantities of the ink set as a color separation ink quantity set associated with each of the plurality of input colors, the determining being made such that a ratio of ink quantities of the color separation ink quantity set represented in the primary color space is equal to a ratio of tone values of the model tone value set for each input color multiplied by the primary coloring factors for the chromatic primary color inks.