An apparatus detects an area specified based on a mark of a specific color out of three primary colors in pigment or three primary colors in light from an image. An other-color-information eliminating unit eliminates information of other colors from a tone level of the specific color by correcting the tone level of the specific color based on tone levels of two colors other than the specific color out of the three primary colors in pigment or the three primary colors in light. An area detecting unit detects the area by specifying the mark based on the tone level from which the information of other colors is eliminated.