In the image processing of color image, color image data are received, and the color image data are corrected to maximize an overlapping quantity of histograms of the image data on a plurality of colors. Alternatively, color image data are received, and histograms of a plurality of colors on the color image data are calculated. Then, color deviation of image is corrected to maximize an overlapping quantity of the histograms. Alternatively, color image data are received, and color fog is detected on the color image data and a color of the color fog is determined. Then, the image data of the color on which color fog is detected is decreased. Alternatively, color fog is detected in an input color image data; and a color of the detected color fog is displayed. Alternatively, color fog of input image is corrected first, and contrast on the image is corrected next.