Group sparsity with overlapping partition functions

This paper introduces a novel and versatile group sparsity prior for denoising and to regularize inverse problems. The sparsity is enforced through arbitrary block-localization operators, such as for instance smooth localized partition functions. The resulting blocks can have an arbitrary overlap, which is important to reduce visual artifacts thanks to the increased translation invariance of the prior. They are moreover not necessarily binary, and allow for non-integer block sizes. We develop two schemes, one primal and another primal-dual, originating from the non-smooth convex optimization realm, to efficiently solve a wide class of inverse problems regularized using this overlapping group sparsity prior. This scheme is flexible enough to handle both penalized and constrained versions of the optimization problems at hand. Numerical results on denoising and compressed sensing are reported and show the improvement brought by the overlap and the smooth partition functions with respect to classical group sparsity.