This invention can generate printed matter on which a multi-valued discrimination image of three values or more cannot be visually confirmed under ordinary light but can be visually confirmed via an infrared camera under infrared light. To this end, a holding unit holds items of color information C1, C2, and C3 each indicating usage amounts of printing materials of three types, used by a printing apparatus, which have a color difference under visible light not more than a pre-set threshold, and which have different infrared light ray absorption rates. When a latent image generating unit generates infrared light ray latent image data of three tones, a discrimination image data generating unit decides one color information item Ci (1≦i≦3) held by the holding unit, and outputs the decided Ci to an output unit which outputs the received pixel values to the printing apparatus.