A device includes converters for converting first image data of an RGB-type into second image data of a YCbCr-type, into third image data of the YCbCr-type, and into fourth image data of the RGB-type, wherein a CbCr-coordinate system has six regions defined by coordinates of a reference color and of six primary colors, and when coordinates of the second image data are located in a region defined by coordinates of the reference color, a first primary color, and a second primary color, the coordinates of the second image data are determined by the coordinates of the reference color, the first primary color, the second primary color, coordinates of a target reference color corresponding to those of the reference color, coordinates of a first target primary color corresponding to those of the first primary color, and coordinates of a second target primary color corresponding to those of the second primary color.