This paper presents a new algorithm for color constant enhancement which adopts the xy chromaticity diagram and consists of two steps. All the "chromatic" colors are first maximally saturated within a certain gamut, the opportune desaturation operation which follows is based on the center of gravity Law of Color Mixture. This prevents the introduction of unnatural colors and, in combination with a suitable manipulation of the brightness value, turns out to increase the image sharpness and to provide more appealing results. Our technique can also be applied to re-rendition of a color image since it can easily simulate the change of the illuminant(s) of the scene portrayed in the image; this could find useful applications in image and video editing. Some examples of the performance of the algorithm are reported and discussed. download full paper