Color image data is stored while being added with an attribute associated with a copy limit of image data in correspondence with a type or level of secrecy to be maintained (e.g., allowing only a specific person to make a full color copy, or to make any copy, of a particular image, or allowing only monochrome copies to be made of a specific image regardless of who is making the copy, etc.) When the color image data is output, an output mode is selected according to the designated type of secrecy to execute image processing and an image output operation, thereby maintaining the desired degree of secrecy of the color image.