Active polygon for object tracking

In this paper, we present a technique for object tracking in image sequences, which includes a novel velocity field estimation for vertex locations of a polygon. In this approach, after capturing boundaries of an object by a polygon from the first few frames of the image sequence, both the spatial segmentation and motion segmentation of a polygonal object can be achieved quickly by involving only the vertex locations and the adjacent edges in the computations. We carry out velocity field estimation at an active polygon vertex using the optical flow constraint on its two adjacent edges. A spatial segmentation phase follows to further refine object's vertex locations estimated by the optical flow. The advantage of our region-based active polygons over continuous active contours in object tracking in video applications is emphasized by provision of a compact representation of object features, particularly for simply connected target shapes, hence will be essential for their tracking.