  In this paper we reconsider the sub-Riemannian cortical model of image
completion introduced by Sarti and Citti in 2003. This model combines two
mechanisms, the sub-Riemannian diffusion and the concentration, giving rise to
a diffusion driven motion by curvature. In this paper we give a formal proof of
the existence of viscosity solutions of the sub-Riemannian motion by curvature.
Results of completion and enhancement on a number of natural images are shown
and compared with other models.
