1. An image forming apparatus with a saving mode in which imaging materials to be used are reduced, comprising: an image processing part that converts image data from which an image will be formed into corresponding image data in an output color space; and an image forming part that foams the image from the image data converted by the image processing part, using the imaging materials; wherein the image processing part reduces a color component of non-dominant (n+m)-component color mixed into a dominant n-component color in the image data converted, where n and m are integers of 1 or greater; and the image processing part converts a process black component produced by the substantially equal amounts of YMC color components among all the YMC color components approaching to the substantially equal amounts to a K color component.