To solve a problem of artificiality in a color printing media when the color is made white in almost a monochromatic expression of cool or warm tone, in which a subtle change in color is important.

First image data is converted into second image data on the basis of correlation of correspondence determined for each combination of color of media and color tone of image. In this case, a relation of a highlight part is so defined that each color tone is made close to ideal chromatic change for each color tone. As a result, even for the highlight part can be changed in color into a natural color tone for every media and every color tone.