PURPOSE: To eliminate unnatural color variation by transforming picture data into a component in average color space in a color space coordinate transformation part, performing necessary processings in each processing part so as to be returned to picture data in a color space coordinate inverse transformation part.

CONSTITUTION: The picture data from a picture data input part 1 is transformed into respective components of brightness, saturation, and hue in the average color space in a color space coordinate transformation part 2. The processings for each component are performed in a brightness processing part 20, a saturation processing part 30, and a hue processing part 40. Further, the inverse transformation is performed in the color space coordinate inverse transformation part 12, and the result is displayed in a picture display part 13.