It is possible to compatibly set multiple “dropout” color ranges and “non-dropout” color ranges and uniquely determine a dropout boundary. An object of the present invention is to greatly conserve maintenance cost of adding a new dropout form after apparatus operations. A conventional technology aims at assuring relation to a predetermined color region, determining the presence or absence of contention, or uniquely settling a dropout boundary. The present invention provides a means for supplying levels to a “dropout” color range and a “non-dropout” color range. A registered color range histogram can be quasi-three-dimensionally visualized so that an operator can make adjustment by viewing a contention determination result and an image.