An original color image is read to generate color image data. The color image data is converted into coordinate data including values associated with a first coordinate value and a second coordinate value in a color space. The first coordinate value is indicative of brightness. It is acquired correction data including values corresponding to the second coordinate value which are determined in accordance with the values included in the coordinate data and associated with the first coordinate value. The coordinate data is corrected with the correction data. A color image is printed with the corrected coordinate data, thereby obtaining a copied image of the original color image.