Three-dimensional gamut mapping using various color difference formulae and color spaces

Gamut mapping is a technique to transform out-of-gamut colors to the inside of the output device's gamut It is essential to develop effective mapping algorithms to realize "WYSIWYG" color reproduction. In this paper, three-dimensional gamut mapping using various color difference formulae and color spaces are considered. Visual experiments were performed to evaluate which combination of color difference formula and color space for gamut mapping was most preferred for five images. The color difference formulae used in the experiments were Delta E-ab *, Delta E-ab*, Delta E-94, Delta E-CMC, Delta E-BFD, and Delta E-wt. The color spaces used in the experiments were CIELAB, CIELUV, CIECAM97s, IPT, and NC-IIIC. A clipping method was used that maps all out-of-gamut colors to the surface of the gamut and no change was made to colors inside the gamut It was found that gamut mapping using Delta E-94, Delta E-CMC, and Delta E-wt were effective in CIELAB color space. For mapping images containing a large portion of blue colors, Delta E-BFD, and Delta E-UV* were found to be more effective. Delta E-ab* was least preferred for all images. With respect to color spaces, gamut mapping performed in the CIELUV color space was superior to any other color spaces for the blue region. We conclude that Delta E-94 in CIELUV and Delta E-BFD in CIELAB are the two most useful combinations of color difference formula and color space for gamut mapping, if we are to apply a single combination universally. (C) 1999 SPIE and IS&T.