Progressive Negative Enhancing Contrastive Learning for Image Dehazing and Beyond

Image dehazing is a pivotal preliminary step in the advancement of robust intelligent surveillance system. However, it is an extremely challenging ill-posed problem, as it faces severe information degradation when accurately restoring the clean image from its haze-polluted counterpart. This paper proposes a novel Progressive Negative Enhancing (PNE) contrastive learning mechanism to fully exploit various types of negative information, thereby facilitating the traditional positive-oriented objective function for image dehazing. The proposed method can progressively update the negative samples during model training, to steadily squeeze the restored image towards its desired clean target from various directions. Furthermore, considering the image dehazing task as a many-to-one feature mapping problem, we also make an early effort to enhance the robustness of the dehazing model under variational haze densities. Specifically, a novel density-variational dehazing network is proposed to be optimized under the consistency-regularized framework using the proposed PNE learning mechanism. The consistency regularization ensures consistent output given multi-level degraded hazy images, thereby significantly enhancing the robustness of the model in dealing with various hazy scenarios. Extensive experiments demonstrate that the proposed method exhibits superior performance over existing state-of-the-art methods. It achieves average PSNR boosts of 0.60 dB, 0.28 dB and 0.82 dB on dehazing, deraining and desnowing tasks, respectively.