(A) chromatic color constancy model for three dimensional objects based on human visual and illuminant perception

Abstract

This thesis explores color constancy for three-dimensional objects. Color constancy is a human visual characteristic that is able to perceive the intrinsic color of an object independent of illuminant color. In computer vision filed, it is formulated by recovering the constant color descriptor of an object in a scene. In order to recover the constant color descriptor, essential issues include the analysis of a scene, the estimate of illuminant information color and direction, the development of model for recognizing object color through analyzing physical phenomena such as specular reflection, interreflection, shadow, and shading. The constant descriptor has not been successfully described yet in computer vision group. One of main reasons is a lack of model enough to relate the physical phenomena to scene characteristics. Moreover, algorithm for estimating of illuminant color in a real scene has not been developed until now. To solve the first problem, this thesis proposes the chromatic model named by the "tetra-chromatic model". Since the tetra-chromatic model enables to analyze highlight as well as interreflection, it has more generalized concept than previous approaches. To constructing the tetragonal model, this thesis derives a reflection model for multi-illuminants by considering the interreflection as secondary illuminant. Because the colors observed on an object with both the highlights and the interreflection have volumetric distribution on RGB color space, it is impossible to analyze it and to obtain a constant color for the object. To solve this problem, we adapt two dimensional color space chromaticity coordinates as the basic color space for color analysis. We found that the reflection model for a three dimensional object with the highlight and the interreflection formed a tetragon in the chromaticity space, which was referred to the "tetragonal model" in this thesis. The tetragonal-model enables to recognize both specular reflection and interref...