Commentary Paper on "Shadow Removal in Indoor Scenes"

The technique proposed in this paper combines three algorithms for shadow removal in indoor scenes. First algorithm takes an advantage of the assumption on the chromaticity consistency: the ambient light chromaticity is approximately the same as the chromaticity of the diffuse light. Magnitude of differences between chromaticity values of shadow and non-shadow regions for different hue values are different for RGB and HSV color spaces so both spaces are used in conjunction by setting thresholds on these differences. Second algorithm takes a potential shadow region and applies a threshold on the intensity reduction of each pixel and its neighboring pixels. It is ensured that the shadow regions are above minimum specified size. The third algorithm uses a threshold on the intensity reduction as a result of light being blocked by moving objects. This reduction depends on the background geometry, light source, moving object size, and position. The threshold reduction caused by a shadow is obtained by manually specifying shadow regions and recording these values which are later used for shadow removal in the same scene.