Recovery of Chromaticity Image Free from Shadows via Illumination Invariance

A recent method for recovering a greyscale image that is free from shadow effects is extended such that the recovered image is a colour image, in the sense that 2-dimensional chromaticity information is recovered. First, the effect of lighting change, and thus to a large degree shadowing, is removed by projecting logarithms of 2D colour band-ratio chromaticities into a direction that is independent of lighting change. The resulting 2-vector colour does not contain the contribution of the original lighting in the input image, so this is restored by considering the chromaticity for bright pixels. The resulting image is improved by regression of the chromaticity onto the original image, with promising results.