Improving Color Constancy Using Chromaticity-Line Prior

Color constancy is the ability to remove the effect of illumination on color. Since color constancy is an ill-posed problem, many methods have been proposed based on assumptions to constraint the solution space. However, most existing assumptions require specular pixels or abundant colors, and fail to produce satisfactory results for different scenarios. According to extensive experiments, we observe that the chromaticity distribution of pixels within main color under canonical illumination, which we called canonical pixels, is linear and can also locate the position of illumination under the non-canonical illumination. Therefore, this paper proposes a chromaticity-line prior (CLP) as an additional linear constraint on the ill-posed problem of color constancy. In the calculation of CLP, the simple linear iterative clustering is firstly employed to segment an image into several super-pixel blocks. And the random sampling consensus is utilized to remove non-primary color points and fit the chromaticity-line. Based on the proposed CLP, a color constancy algorithm is implemented correspondingly. Since the main idea of the CLP is to extract the canonical pixels, which is the inherent property of image, the proposed CLP is more general and adaptive in real scenes. The experiments on two public datasets demonstrate that the proposed algorithm not only outperforms state-of-the-art learning-free algorithms, but also achieves results that are competitive to those of learning-based algorithms.