Natural Color Reproduction of an Image with Highlights by Vector Transformation and Non-linear Mapping

©2001, IS&T—The Society for Imaging Science and Technology ject remains invariant with changes in the illumination. The mechanisms that provide color constancy must decompose the reflected light and discount the spectral properties of the illumination in order to establish the colors of the objects in terms of their surface reflectance functions.3–5 Most previous research on the reproduction of natural color images using color constancy has been theoretical, involving the study of mathematical constraints under which color constancy could be possible and analyses of the quantitative properties of previously proposed mechanisms. Recently, however, several realizable constancy algorithms have been developed which can be classified into two categories. The first includes wavelength methods,1–5,17,18 whereas the other involves lightvalue (tri-stimulus values) methods.6,7 Wavelength methods originate from Maloney’s algorithm.1 Maloney developed a computational color constancy algorithm derived from the premise that surface spectral reflectance functions can be approximated by a linear combination of a fixed set of basis functions. In this algorithm, color-constant surface descriptors can be computed if there are more classes of photoreceptors than degrees of freedom in the linear model for surface spectral reflectance. As such, a trichromatic system will be color constant if the spectral reflectance functions are constrained to at most two degrees of freedom. HowIntroduction