Image processing in which input image signals are converted into output image signals represented as a combination of colored and colorless colorant amounts. For each pixel of an input image represented by the input image signal, it is determined whether the pixel belongs to a high or low density range. For each pixel belonging to the high density range, it is specified whether the pixel belongs to a high or low frequency region of the input image. Color conversion with a 1st conversion parameter is applied to an input image signal corresponding to a pixel belonging to the high frequency region, and color conversion with a 2nd conversion parameter is applied to an input image signal corresponding to a pixel belonging to the low frequency region.