Elliptical head tracking using intensity gradients and color histograms

An algorithm Sor tracking a person's head is presented. The head's projection onto the image plane is modeled as an ellipse whose position and size are continually updated by a local search combining the output of a module concentrating an the intensity gradient around the ellipse's perimeter with that of another module focusing on the color histogram of the ellipse's interior: Since these two modules have roughly orthogonal failure modes, they serve to complement one another: The result is a robust, real-time system that is able to track a person's head with enough accuracy to automatically: central the camera's pml, tilt, and zoom in order to keep the person centered in the field of view at a desired size. Extensive experimentation shows the algorithm's robustness with respect to full 360-degree out-of-plane rotation, up to 90-degree tilting, severe but brief occlusion, arbitrary camera movement, and multiple moving people in the background.