Image Fusion With No Gamut Problem by Improved Nonlinear IHS Transforms for Remote Sensing

Abstract—An image fusion method must ideally preserve both the detail of the panchromatic image and the color of the mul-tispectral image. Existing image fusion methods incur the gamut problem of creating new colors which fall out of the RGB cube. These methods solve the problem by color clipping which yields undesirable color distortions and contrast reductions. An im-proved nonlinear IHS (intensity, hue, saturation; iNIHS) color space and related color transformations are proposed in this paper to solve the gamut problem without appealing to color clipping. The iNIHS space includes two halves, one being constructed from the lower half of the RGB cube by RGB to IHS transformations, and the other from the upper half of the RGB cube by CMY to IHS transformations. While incurring no out-of-gamut colors, desired intensity substitutions and additions in substitutive and additive image fusions, respectively, are all achievable, with the saturation component regulated within the maximum attainable range. Good experimental results show the feasibility of the proposed method. Index Terms—Clipping, gamut problem, image fusion, im-proved nonlinear IHS (iNIHS) color space, multispectral image, panchromatic image. I