To conveniently trim image parameters about light and darkness and color of an image read by an image reader, etc.

An image display area PI is provided. Three control bars CB0 to CB2 that are slide-type marks are provided. Check buttons BG and BT that are selected alternatively are provided and are made to correspond to the gain and tone respectively. The bars CB0 to CB2 are made to correspond to the gain or tone of RGB according to the selection of the buttons BG and BT. The positions of the line segments of the bars CB0 to CB2 are made to correspond to the values of the gain or tone of the RGB selected by the buttons BG and BT. Each image parameter is set by horizontally shifting the knob- shaped marks CM0 to CM2 of the bars CB0 to CB2 with a mouse.