A Technique for Compensating Light Source Direction in Face Recognition Applications

A process to obtain the directional component of the main light source illuminating a human face in an image is described. In the first step of this process, two measures using low resolution data are obtained from the image. The value of these measures is then compared with those obtained from a synthetic model illuminated from different directions. This process, however, is not sufficient to indicate a single direction as is proved using a simplified model for face parts. An additional step is required to break the tie by using high frequency data. Once the light direction is determined, correction values are added to the image pixels to obtain an approximation of the face imaged under standard illumination conditions thereby making recognition much easier.