To output an image having less discomfort by use of overprint and trapping.

With respect to a color image formed using a plurality of fundamental colors, as color data on the adjacent region of an object included in the image, the number of colors or the print quantity of colors expressed in the adjacent region is obtained (#11). Then, as processing to be performed on the object to reduce unnaturalness near the boundary of the object, trapping or overprint is selected (#12) on the basis of the obtained color data and executed (#13).