Basis image decomposition for outdoor lighting estimation

Based on the theory of the basis image decomposition of the sunlight and the skylight for fixed outdoor scenes, we prove that three images captured with the same sun position under different weather conditions show linear correlation. Therefore, the basis image equations are the systems of under-constraint so that they can not be solved automatically. In this paper, we present the algorithm of solving basis images using four images with two sun positions under two kinds of weather conditions. In addition, the hue consistency of pixels in the sun area between the basis images of the sunlight and the skylight is used to optimize basis images and illumination parameters. The experimental results show that basis images can be solved automatically and the original images can be reconstructed accurately according to basis images and illumination parameters. Hence, it is suitable for augmented reality with high quality.