1. An image processing apparatus for processing first image data including first color data expressing values of picture elements for a plurality of colors to obtain second image data including second color data expressing values of the picture elements for the plurality of colors, the image processing apparatus comprising: an image processing unit for processing the first image data to obtain third image data; a hue region data calculator for using the first image data to calculate hue region data valid for particular hues among a plurality of hues; a data combining coefficient calculator for calculating a data combining coefficient from the hue region data, wherein said data combining coefficient represents a ratio for combining the first image data and the third image data; and an image data combiner for combining the first image data and the third image data according to the combining ratio to obtain the second image data.