Patent ID: 7196823

Claim:
A method of creating a lookup table indicating a relationship between each lattice point in an input color space and a color signal set in a target color space, the input color space being defined by several color components whose total number has a first value, the target color space being defined by several color-signal components, whose total number has a second value greater than the first value by a difference number and each of which has one of a plurality of discrete values, the input color space being divided into a lattice to define a plurality of lattice points indicative of a plurality of lattice color sets, each lattice color set being constructed from color values of the several color components, a color value of each color component in the lattice color set having one of another plurality of discrete values, the color signal set being constructed from color values of the several color-signal components, the method comprising the steps of: determining one color signal set for each lattice point in the input color space, a color reproducible range being defined in the input color space and being determined dependently on a value of at least one color-signal component in the determined color signal set, the total number of the at least one color-signal component being greater than or equal to the difference number, the color reproducible range containing the subject lattice point and a color point of the determined color signal set therein, the subject lattice point being the closest to the color point of the determined color signal set within the color reproducible range; and setting, for each lattice point, the one color signal set determined for the subject lattice point, thereby creating the lookup table.