A COLOR CONSTANCY MODEL FOR ADVANCED TELEVISION CAMERAS

Abstract

In high-fidelity color sensing, one may attempt to use recorded video image data from an electronic camcorder to generate a rendering that appears the same as the original image did at the time of acquisition. To achieve the goal, a color constancy mechanism is proposed to perceive the image color from the strengths of three RGB responses of a color camera or the like, independent of the color of the light illuminating the object. Being able to extract the color descriptors that are independent of the illumination is desirable because of the varity of the situation in which color is important but illumination conditions cannot be controlled. The first step of our method is to use a finite dimensional linear model to estimate the color signals. We have shown that any color signal can be characterized as a linear combination of four principal component basis functions. Once the color signals have been estimated, the unknown illuminant can be determined by the Tominaga and Wandell's estimation method which is based on a dichromatic model. In color constancy, the knowledge of surface reflectance helps in determining the canonical color descriptors despite the variation in the spectral power distribution of the ambient light. It is shown that the estimate of surface reflectance is derived from both the estimated color signal and illuminant straightforwardly. The model of a combination of the estimations of the surface spectral reflectance and the color signals can be employed in designing a color constancy electronic video camera which indeed improves the shortcomings of the traditional video camcorders.