An Infeasible Primal-dual Algorithm for Tv-based Inf-convolution-type Image Restoration

In this paper, a primal-dual algorithm for TV-type image restoration is analyzed and tested. Analytically it turns out that employing a global L-regularization, with s > 1, in the dual problem results in a local smoothing of the TV-regularization term in the primal problem. The local smoothing can alternatively be obtained as the infimal convolution of the `r-norm, with r−1 + s−1 = 1, and a smooth function. In the case r = s = 2, this results in Gauss-TV-type image restoration. The globalized primal-dual algorithm introduced in this paper works with generalized derivatives, converges locally at a superlinear rate and is stable with respect to noise in the data. In addition, it utilizes a projection technique which reduces the size of the linear system that has to be solved per iteration. A comprehensive numerical study ends the paper.