Single nighttime image dehazing based on unified variational decomposition model and multi-scale contrast enhancement

Most of existing dehazing methods are unable to deal with nighttime hazy scenarios well due to complex degraded factors such as non-uniform illumination, low light, glows and hazes. To obtain high-quality image under nighttime haze imaging conditions, we propose a single nighttime image dehazing framework based on a unified variational decomposition model and multi-scale contrast enhancement to simultaneously address these undesirable issues. First, a unified variational decomposition model consisting of three regularization terms is proposed to simultaneously decompose a nighttime hazy image into a structure layer, a detail layer and a noise layer. Concretely, we employ ℓ1 norm to constrain the structure component, adopt ℓ0 sparsity term to enforce the piece-wise continuous of the residual of the gradients between the detail layer and the modified glow-free image, and use the Frobenius norm to estimate the noise layer. Next, the hazes in the structure layer are removed by inversing the physical model and the effective details in the texture layers are enhanced while the amplified noises are suppressed in a multi-scale fashion. Finally, the dehazed structure layer and the enhanced detail layers are integrated into a haze-free image. Experiments demonstrate that the proposed framework achieves superior performance on nighttime haze removal and noise suppression compared with state-of-the-art dehazing techniques.