Robust and fast computation of edge characteristics in image sequences

In this paper we consider a non-parametric analytical model of the intensity for a curved edge, and derive the relations between the image data and some local characteristics of the edge, in the discrete case. In order to identify this model we also study how to develop high order non-biased spatial derivative operators, with subpixel accuracy. In fact, this discrete approach corresponds to the notion of spatio-temporal surfaces in the continuous case, and provides a way to obtain some of the spatio-temporal parameters from an image sequence. An implementation is proposed, and experimental data are provided.Computed characteristics are subpixel localization, normal displacement between two frames, orientation and curvature, but the method is easy to extend to other geometrical or dynamical parameters of the edge.Results derived in this paper are always valid for step-like edges, but computation of orientation and curvature are also valid for edges with more general profiles.