Here a size restriction on the time step τ = ∆t has to be imposed to guarantee the stability of the numerical solution. This is the main drawback of the time marching method, the problem being that due to its high nonlinearity, τ must be chosen very small which implies a large number of iterations to reach a meaningful solution. One option is to accelerate this method using the ideas developed in [20]. However, even in that case the cpu-time consumed by the resulting algorithm is still not appropriate for large images.