Specularity Factorization for Low-Light Enhancement

Low Light Enhancement (LLE) is an important step to enhance images captured with insufficient light. Several local and global methods have been proposed over the years for this problem. Decomposing the image into multiple factors using an appropriate property is the first step in many LLE methods. In this paper, we present a new additive factorization that treats images to be composed of multiple latent specular components that can be estimated by modulating the sparsity during decomposition. We propose a model-driven learnable RSFNet framework to estimate these factors by unrolling the optimization into network layers. The factors are interpretable by design and can be manipulated directly for different tasks. We train our LLE system in a {\em zero-reference} manner without the need for any paired or unpaired supervision. Our system improves the state-of-the-art performance on standard benchmarks and achieves better generalization on multiple other datasets. The specularity factors can supplement other task specific fusion networks by inducing prior information for enhancement tasks like deraining, deblurring and dehazing with negligible overhead as shown in the paper.