N-White Balancing: White Balancing for Multiple Illuminants Including Non-Uniform Illumination

In this paper, we propose a novel white balance adjustment for multi-illuminant scenes, called “N-white balancing,” in which
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source white points are mapped into a ground truth one. Most white balance adjustments focus on adjusting single-illuminant scenes. Several state-of-the-art methods for adjusting multi-illuminant scenes have been proposed, but they need to know the number of segments or the number of light sources in advance. Multi-color balance adjustments have been investigated to improve the performance of white balancing, but they also suffer from color distortion due to the rank deficiency problem. In contrast, the proposed method, N-white balancing, can correct multi-illuminant scenes even when we do not know the exact number of segments or light sources in a scene. In an experiment, the proposed method was demonstrated to outperform state-of-the-art methods under various illumination conditions such as single and multiple illuminants including non-uniform light sources.