Supervised Dictionary Learning with Smooth Shrinkage for Image Denoising

The dictionary-based method is an important approach to image denoising. In the existing methods, the dictionary is either pre-defined or learned adaptively from the data under certain constraints such as sparsity or orthogonality, which often leads to an approximation solution. In this paper, we propose a novel supervised dictionary learning model with smooth shrinkage for image denoising. By incorporating the dictionary learning into the denoising target, our model is trained in a task-driven fashion without the need of explicit constraints. We analyze the proposed model theoretically and show that it tends to learn sparse and orthogonal dictionaries, which is further verified empirically. Experimental results on four different noise levels demonstrate the effectiveness of our model both quantitatively and visually in comparison with the classical dictionary-based denoising methods.