A method to use most of the colors that are available when rendering color images where a limited number of colors are available such as rendering images in VGA mode. A group management database stores a group property, thereby a quantity of prints printed by a laboratory and information provided by a terminal can be determined based on the group property and the number of the members, for example. 30\xd7\u2264T\u22643\u2062\u03bb4\u2062\u2062n+0. The domain forming member is formed with irregular parts including a first irregular part having an enlarged width, a second irregular part having a reduced width, and an external irregular part, which is closest to the first region of the irregular parts formed in the second region and has an enlarged width.