Front propagation and level-set approach for geodesic active stereovision

Given a weakly calibrated stereo system and a virtual 3D surveillance plane specified by any 3 points given by an external operator we describe a framework for matching complex 2D planar curves lying at the intersection of the 3D surveillance plane and the 3D scene being observed. This important information may then be used to know which parts of the objects being observed are between the stereo system and the virtual 3D surveillance plane, and which parts are behind the 3D virtual surveillance plane i.e. outside a security zone specified around the stereo system. Using an energy minimization based approach, we reformulate this stereo problem as a front propagation problem. The Euler Lagrange equation of the designed energy functional is derived and the flow minimizing the energy is obtained. This original scheme may be viewed as a geodesic active stereo model which basically attract the given curves to the bottom of a potential well corresponding to pixels having similar intensities. Using the level set formulation scheme of Osher and Sethian (1988), complex curves can be matched and topological changes for the evolving curves are naturally managed. The final result is also relatively independent of the curve initialization. Promising experimental results have been obtained on various real images.