An image in which at least one color component among a plurality of color components in an input color image has a resolution lower than that of the other color components is held as a base image. A rectangular region that includes an object image is extracted, a region of the object image and a region of a background image are specified in the rectangular region, and fill-up processing of the specified object image is executed in the base image. Fill-up processing executed at a boundary between the object image and the base image differs from fill-up processing executed at a boundary between the object image and the background image.