Retinex-Based Variational Framework for Low-Light Image Enhancement and Denoising

Low-light image enhancement is an important task in the domain of computer vision. Images taken under insufficient lighting conditions manifest low visibility and unknown noises which disrupt image contents and pose considerable challenges for low-light image enhancement. Most of Retinex-based methods usually attempt to design different priors on the gradient of both illumination and reflectance. However, noises can be involved in the Retinex-based models. To address the problem, we explore the problem of low-light image restoration through joint contrast enhancement and denoising. We propose a Retinex-based variational model for low-light image enhancement that effectively generates a noise-free image, yet proves to generalize well to diverse light-conditions. First, we present a simple constraint on the fidelity term between the fractional derivative of an observed image and the fractional derivative of the recomposed one which is the product of the reflectance and illumination. This strategy aims to model spatial consistency to preserve natural variation. Second, we introduce a weighted regularization term for the reflectance that can remove noise with a adaptive texture map. We evaluate our proposed approach using three challenging datasets: NPE, LOL and GladNet. Extensive experiments demonstrate that our proposed method outperforms other competing methods in terms of visual quality and quantitative comparisons.