White Patch Gamut Mapping Colour Constancy

The White-Patch method, one of the first colour constancy methods, estimates the light source colour from the maximum response of the different colour channels. However, it has been eclipsed by the advent of more advanced physical or statistical methods, as well as complex learning based methods. Recently, a new independent line of work claims that the simple idea of using maximum pixel values is not as naive as it seems, but can also be made to perform very well via some manipulations. The bright areas of images can include highlights and specularity as well as white surfaces or light sources, and indeed all may be helpful in the illumination estimation process. In this paper, we define the White Patch Gamut as a new extension to the Gamut Mapping Colour Constancy method, comprising the bright pixels of the image. Adding new constraints based on the possible White Patch Gamut to the standard gamut mapping constraints, a new combined method outperforms gamut mapping methods as well as other wellknown colour constancy methods. The new constraints that are brought to bear are powerful, and indeed can be more discriminating than those in the original gamut mapping method itself.