Method and apparatus for color conversion

摘要

The present invention relates to a method and apparatus applied to a widely-used and high-speed color conversion which is utilized in a color printer, a color display apparatus and the like, and provides a novel three-dimensional interpolation operation by use of a triangle-pole shaped interpolation unit-space. Input color signals R,G, and B are converted into lightness signal Y and chromaticity signals Cr, Cb which constitute a three-dimensional space. This three-dimensional space is dissected into rectangular parallelopipeds and is further divided into two prisms having base planes parallel to the chromaticity plane CrCb. A prism judging section 207 judges which of prisms an input color is involved in. There are provided a plurality of color conversion table memories 210 DIFFERENCE 215 which store output values corresponding to input values constituting respective points of the prism and difference values of mutual output colors and further difference values of mutual difference values. Stored data in respective color conversion table memories 210 DIFFERENCE 215 are weighted by lower-bit signals 205, 206 of the input color signals in multipliers 219, 220, 226, 227, and 230. Then, these data are added in adders 220, 221, 228, 229, and 231 so as to accomplish a linear interpolation using output values of six vertices which constitute the prism.