A combination of a latent-image pattern which forms a latent-image part and a background pattern that forms a background-image part is determined so that the latent-image part and background-image part have equal print densities. The determined latent-image pattern and background pattern, color information used to determine a color of the copy-forgery-inhibited pattern image, input image information as an image to be processed, copy-forgery-inhibited pattern basic information used to designate the latent-image part and background-image part, and camouflage region designation image information used to designate a camouflage region are input. A copy-forgery-inhibited pattern image is generated on the basis of the input information.