A data processing system for performing face detection on a stream of frames of image data, the data processing system comprising: a face detector configured to detect a first face candidate in a first frame by performing face detection within first search tiles defined for the first frame; a color measurement unit configured to calculate a set of color parameters including an average color of the first face candidate expressed according to a predefined color space; a transformation unit configured to: transform a second frame into the predefined color space, one of the axes of the color space being substantially oriented in the direction of maximum variation according to a predetermined distribution of skin color; and form a skin color probability map for the second frame by calculating the probability that a given color is a skin color from a measure of the color space distance of that color from the calculated average color; and a search tile generator configured to generate second search tiles based on the skin color probability map for use by the face detector, the second search tiles defining areas of the second frame within which the face detector is to perform face detection so as to detect one or more second face candidates in the second frame.
Skin colour probability map