Multi-modal system for locating heads and faces

We designed a modular system using a combination of shape analysis, color segmentation and motion information for locating reliably heads and faces of different sizes and orientations in complex images. The first of the system's three channels does a shape analysis on gray-level images to determine the location of individual facial features as well as the outlines of heads. In the second channel the color space is analyzed with a clustering algorithm to find areas of skin colors. The color space is first calibrated, using the results from the other channels. In the third channel motion information is extracted from frame differences. Head outlines are determined by analyzing the shapes of areas with large motion vectors. All three channels produce lists of shapes, each marking an area of the image where a facial feature or a part of the outline of a head may be present. Combinations of such shapes are evaluated with n-gram searches to produce a list of likely head positions and the locations of facial features. We tested the system for tracking faces of people sitting in front of terminals and video phones and used it to track people entering through a doorway.