Two-step multi-illuminant color constancy for outdoor scenes

This paper proposes a novel two-step multi-illuminant algorithm for color constancy in outdoor scenes. We adopt different color constancy approaches for both primary and secondary illuminations. In the first step, an input image is white-balanced entirely using the existing single-illuminant color constancy method. Next, we extract the secondary illumination region, which typically corresponds to a shaded region in outdoor scenes. Finally, the shaded region is corrected by the guidance of the Planckian locus theory. Experimental results show that the proposed algorithm can achieve much smaller angular error than conventional multi-illuminant methods while color artifact is alleviated.