Object segmentation and tracking are improved by including directional information
to guide the placement of an active contour (i.e., the elastic curve or 'snake')
in estimating the object boundary. In estimating an object boundary the active
contour deforms from an initial shape to adjust to image features using an energy
minimizing function. The function is guided by external constraint forces and image
forces to achieve a minimal total energy of the active contour. Both gradient strength
and gradient direction of the image are analyzed in minimizing contour energy for
an active contour model.
