Optimizing Gamut Mapping : Lightness and Hue Adjustments(Gamut Mapping II)(Report on CIC)

抄録

This study evaluates gamut mapping algorithms with different mapping types and mapping directions. Among these are the method of mapping colors towards a focal point as well as the newly developed relative lightness change (RLC) technique. The latter maps colors along curved lines and enables the direct use of cylindrical coordinates lightness, chroma, and hue for the mapping, regardless of the mapping direction. Additionally, hue adjustments are applied. The paper discusses issues of gamut mapping such as the mapping space, the coordinate system within the space, and gamut boundary description. Psychophysical experiments are described which were conducted to evaluate the reproduction of monitor images on a device with a clearly smaller color gamut. All images were viewed on the monitor. The algorithms were dependent on the image gamuts. The experiments show that the RLC method performs superior over the centroid mapping. Moreover, the optimum mapping direction was RLC5O which means a slight adaptation of lightness. The best mapping type was pure clipping, regardless of the mapping direction. These results help understanding the mechanisms of gamut mapping and support further developments and research in color image reproduction.