A tone setting screen that includes a tone specifying area 110 for specifying a color tone of a monotone image using a single specification point is disclosed. A monotone image tone is determined according to the position of the specification point specified in the tone specifying area 110. The tone specifying area 110 is defined on the a* b* plane in the L*a*b* color space, where three reference tone points Pneutral, Pwarm, and Pcool, for the neutral, warm, and cool tones are disposed linearly in advance in the tone specifying area 110.