Patent ID: 8164597

Claim:
A color conversion circuit for converting input color data into output color data, the input color data being positioned within a three-dimensional color space, which is divided in a plurality of unit cubes having a fixed dimension, at a position specified by coordinates of the input color data, the conversion circuit comprising: a three-dimensional look-up table that stores conversion coefficients at respective vertexes of the plurality of unit cubes; a substitution circuit that reads conversion coefficients at vertexes of one of the unit cubes in which the input color data is positioned from the three-dimensional look-up table and performs a substitution of some of the conversion coefficients read from the look-up table with substitute conversion coefficients expressed by other ones of the conversion coefficients read from the look-up table; and an interpolation circuit that performs an interpolation from the conversion coefficients after the substitution to generate converted coordinates of the output color data using volumes of rectangular parallelepipeds that divide the one of the unit cubes such that each of the rectangular parallelepipeds shares the input color data as a vertex, wherein: each of the conversion coefficients at vertexes on either end of a diagonal line placed on a gray axis of the color space of each of the unit cubes on the gray axis has three components equal with each other, the vertexes of the each of the unit cubes on the gray axis include, in addition to the vertexes on the either end of the diagonal line, six other vertexes, and when the one of the unit cubes has the diagonal line placed on the gray axis, the substitution circuit groups the six other vertexes in two groups depending on which of the vertexes on the either end of the diagonal line is closer, selects at least one of the vertexes from each of the two groups, and performs the substitution of the conversion coefficients at the selected vertexes such that a sum of the conversion coefficients after the substitution at the vertexes in each of the two groups is expressed by a linear combination of the conversion coefficients at the vertexes on either end of the diagonal line.