Automatic Extraction and Tracking of Complex Contours

In this paper, we propose an algorithm to extract and track complex contours with occlusions such as the contours of the human body. In this algorithm, complex contours are assumed to be composed of contour segments which have smooth variation of the intensity gradient normal to the contour direction. Moreover, the contour segments are modeled using B splines, and contours in the image are extracted and tracked by the contour segments. In the first frame, contour segments are extracted using only the edge pixels. In the tracking of contour segments of the next frame, we use Snakes. For frames after the second frame, the contour segments are redetected using the tracking result and edge pixels. After that, extraction and tracking are repeatedly applied to each frame. Moreover, a method of classification of contour segments which is based on movement is described and the possibility of human action description is investigated. Finally, experimental and classification results obtained by means of this algorithm on synthesized and real images are given.