An image processing apparatus which processes a plurality of supplied color image signals and outputs the processed signals to an image forming apparatus. The image processing apparatus comprises a conversion section which converts the supplied color image signals to a plurality of color signals, a discrimination section which discriminates attributes of the supplied color image signals, a determination section which determines, based on the color signals converted by the conversion section, a plurality of color signals outside a color gamut capable of image formation in the image forming apparatus, a processing section which changes the color signals outside the color gamut determined by the determination section to a plurality of color signals in the color gamut of the image forming apparatus in accordance with a discrimination result of the discrimination section, and an output section which matches the color signals from the conversion section and the color signals from the processing section and delivers the matched result to the image forming apparatus.