Color Constancy: Algorithm and Hardware Architecture Design

• Main Authors: Tung-Yang Wu, 吳東陽
• Other Authors: Shao-Yi Chien
• Format: Others
• Language: en_US
• Published: 2008
• Online Access: http://ndltd.ncl.edu.tw/handle/71628149939660026643

碩士 === 國立臺灣大學 === 電子工程學研究所 === 96 === Abstract Humans are able to recognize the color of objects independently of the light sources, which is called as color constancy. In a digital still camera, a sensor is used to measure the reflected light, and the measured color at each pixel varies according to the color of the illuminant. Therefore, the resulting colors may not be the same as those perceived by users. Many algorithms have been developed to solve the color constancy problem, which is sometimes also called as auto white balance. Since digital cameras and mobile phones equipped with cameras became more and more popular in recently years, the selection of color constancy algorithms for realtime system implementation is an important issue. In this thesis, we first provide a comprehensive introduction to the field of color constancy, where the major color constancy algorithms are described. The performance of these algorithms are then evaluated, and the hardware cost of some algorithms are analyzed with a proposed system framework. Furthermore, based on the analysis results, we also propose a new algorithm by taking advantages of existing Gamut Mapping and modified Gary World algorithms. Gamut Mapping algorithm is employed when the number of recognized illuminants is small enough, and modified Gray World algorithm is employed for other cases. After comparing with other color constancy methods with a large date sets of images recording objects under different light sources, the experiments show that the proposed color constancy algorithm achieves the best performance with acceptable hardware cost.