Color gamut mapping based on a perceptual image difference measure

Gamut mapping is a color transformation technique to solve a problem caused by mismatch of gamuts among imaging devices. One plausible goal of gamut m apping is to find a reproduction that is perceptually closest to the corres ponding original image when an exact color matching is not possible. Severa l measures to quantify, the perceptual difference between images have been proposed and applied to the gamut mapping problem. However most of the meas ures, such as average color difference, are applied on a pixel-wise basis a nd show poor correlation with human visual perception. This article describ es a model of the perceptual image difference for a given pair of images wh ich takes the human's contrast sensitivity into account and applies the mod el to a gamut mapping for generating a reproduction with minimum perceptual image difference. The model has a multispatial-frequency channel structure with tunable peak gains for each channel, which are determined by psychoph ysical experiments, so that the model output fits the observer's sensitivit y to the image difference A gamut-mapped image with minimum perceptual imag e difference is obtained by an iterative minimization process. To evaluate the proposed method, subjective evaluation experiments are performed to con struct ratio scalds that measure perceptual image difference of gamut-mappe d reproductions generated by the proposed and pixel-wise methods. Results s how that the reproductions by the proposed method are perceived as perceptu ally closest to the original, and the model's estimate of perceptual differ ence correlates better with the experimentally measured perceived image dif ference than other pixel-wise measures. (C) 1999 John Wiley & Sons, Inc.