Color gamut mapping techniques for color hard copy images

摘要

Color gamut mapping is required whenever two imaging devices do not have coincident color gamuts or viewing conditions. Two major gamut mapping techniques include lightness and chroma manipulations. Lightness mapping accounts for differences in white level, black level, and viewing conditions while chroma mapping accounts for differences in gamut volume.rnAs a three dimensional space in which color gamut mapping is implemented, the 1991 Hunt model of color appearance was used utilizing dimensions of lightness, chroma, and hue. This model accounts for viewing conditions in addition to the usual device independent specification. The mapping techniques were applied to back-lit photographic transparencies in order to reproduce images using a dye diffusion thermal transfer printer. As the first experiment, a lightness mapping experiment was performed. Three different lightness mapping techniques, a linear technique and two non-linear techniques, were tested for four images. The psychophysical method of paired comparison was used to generate interval scales of preferred color reproduction. In general, the preferred technique depended on the amount of lightness mapping required and on the original image's lightness histograms. For small amounts of compression, the preferred technique was a clipping type. For large amounts of compression, the preferred technique was image dependent; low preference was caused by loss of detail or apparent fluorescence of high chroma image areas.