Skin detection in video under changing illumination conditions

Techniques for colour-based tracking of faces or hands often assume a static skin colour model. However, skin color perceived by a camera can change when lighting changes. In common real environments multiple light sources impinge on the skin. Therefore, for robust skin pixel detection, a dynamic skin colour model that can cope with the changes must be employed. We show that skin detection in video can be enhanced by exploiting the knowledge of the range of possible skin colours for the camera used. In normalized colour coordinates this range has a distinct shape we call the skin locus. We developed an adaptive histogram backprojection technique where the skin colour model is updated by pixels in the search region which fall in the skin locus. We demonstrate increased detection capability with webcam videos of faces taken successively under daylight, incandescent lamp, fluorescent light and a combination of these light sources.