1. An apparatus comprising: a processor; a memory configured to store a program instructing the processor to function as: a detection component configured to detect a semi-transparent object including opaque pixels and transparent pixels; a changing component configured to change color values of the opaque pixels of the detected semi-transparent object; an overlaying component configured to overlay the semi-transparent object whose opaque pixels have the changed color values on another object to obtain an overlaid image; and a dither process component configured to apply a dither matrix to the overlaid image, the overlaid image including pixels corresponding to the opaque pixels and pixels corresponding to the transparent pixels, wherein the pixels of the overlaid image corresponding to the opaque pixels have the changed color values, and the pixels of the overlaid image corresponding to the transparent pixels have color values that are the same as the color values of the another object.