To reduce the number of pixels of color conversion objects, without having drastically to damage image quality and to accelerate processing by simultaneously performing compressing processing and color conversion processing of an image.

A high-frequency component processing part performs very simple (i.e., a few calculations) color conversion in a low image quality color converting part 21 if it is needled and subsequently, performs frequency conversion in a high frequency component calculating part 22. A low-frequency component processing part first samples an original image due to thinning processing by an LPF(low-frequency pass filter) 23 and a subsampling part 24 and obtains a reduced image with a small number of pixels. A high quality color converting part 25 performs high (i.e., a large amount of calculation) color conversion of the reduced image. Then, a low-frequency component calculating part 26 performs frequency conversion of the reduced image, that has been subjected to color conversion. A value obtained by the frequency conversion is sent to a compositing multiplexing part 27 and used for a frequency component value obtained by the part 22 as the value of a low pass component.