There is disclosed an image processing apparatus for generating an address based on a difference (MAXnullMIN) between a maximum value MAX and a minimum value MIN among signals CMY indicating three primary colors of a color image for each pixel, and generating a black ink signal based on data read from a lookup table in which the data is read from the generated address, so that a black ink strength is independently set with respect to density and chroma of the image. Moreover, the lookup table with the black ink signal and an undercolor signal stored therein has a storage capacity of a number obtained by totaling a number at which the difference (MAXnullMIN) between the maximum value MAX and the minimum value MIN is an integral multiple of a predetermined value and a number at which the difference is other than the integral multiple and the maximum value MAX is equal to a maximum value of a defined region. Thereby, all combinations of the maximum value MAX and minimum value MIN are linearly interpolated without disposing any storage region.