Patent ID: 7177465

Claim:
A method of compressing/extending a color reproducing space for transforming a color reproducing space of a first image input/output device into a color reproducing space of a second image input/output device, comprising: a chroma compressing/extending step which compresses or extends chroma of a color gamut of the first image input/output device represent within the same hue plane in a uniform color space in said same hue plane; a lightness correcting step for correcting lightness of the color gamut compressed or extended by the chroma compressing/extending step, said lightness correcting step not executing correction of the lightness when a chroma value is 0, correcting a highest chroma point having a maximal chroma value of said compressed or extended color gamut to a specified point in the color gamut represented in said same hue plane of the color reproducing space of said second image input/output device when said chroma value is the maximal chroma value and correcting the lightness such that a correction amount of the lightness changes in a non-linear manner as the chroma value becomes higher when the chroma value is within a range of from more than 0 to less than said maximal chroma value; and a lightness compressing/extending step of compressing or extending the color gamut which has been processed by said chroma compressing/extending step and said lightness correcting step into within the color gamut of said second image input/output device in said same hue plane.