A color conversion apparatus to output image data to a printer obtains roughness data to indicate the roughness of each pixel in an image expressed by the image data, derives a reduction ratio of a color gamut in each pixel according to a roughness of each pixel in the roughness data, changes color gamut data indicating for the printer on a substantially flat surface according to the derived reduction ratio to derive color gamut data in each pixel, and then performs color conversion on each pixel in the image data using the derived color gamut data.
