When a lightness level expressed by a selected pixel value is equal to or larger than a threshold, the use amounts of respective color materials of a first color material group, and those of respective color materials of a third color material group are stored in a memory in association with the selected pixel value. On the other hand, when the lightness level expressed by the selected pixel value is smaller than the threshold, the use amounts of respective color materials of the first color material group, and those of respective color materials of a second color material group are stored in the memory in association with the selected pixel value.