说明：  The sparsity of signals and images in a certain trans-form domain or dictionary has been exploited in many applications in signal and image processing. Analytical sparsifying transforms such as Wavelets and DCT have been widely used in compression standards. Recently, synthesis sparsifying dictionaries that are di-rectly adapted to the data have become popular especially in appli-cations such as image denoising, inpainting, and medical image re-construction.