Deep Convolutional Dictionary Learning for Image Denoising

Inspired by the great success of deep neural networks (DNNs), many unfolding methods have been proposed to integrate traditional image modeling techniques, such as dictionary learning (DicL) and sparse coding, into DNNs for image restoration. However, the performance of such methods remains limited for several reasons. First, the unfolded architectures do not strictly follow the image representation model of DicL and lose the desired physical meaning. Second, handcrafted priors are still used in most unfolding methods without effectively utilizing the learning capability of DNNs. Third, a universal dictionary is learned to represent all images, reducing the model representation flexibility. We propose a novel framework of deep convolutional dictionary learning (DCDicL), which follows the representation model of DicL strictly, learns the priors for both representation coefficients and the dictionaries, and can adaptively adjust the dictionary for each input image based on its content. The effectiveness of our DCDicL method is validated on the image denoising problem. DCDicL demonstrates leading denoising performance in terms of both quantitative metrics (e.g., PSNR, SSIM) and visual quality. In particular, it can reproduce the subtle image structures and textures, which are hard to recover by many existing denoising DNNs. The code is available at: https://github.com/natezhenghy/DCDicL_denoising.