Learning to Decompose and Restore Low-light Images with Wavelet Transform

Low-light images often suffer from low visibility and various noise. Most existing low-light image enhancement methods often amplify noise when enhancing low-light images, due to the neglect of separating valuable image information and noise. In this paper, we propose a novel wavelet-based attention network, where wavelet transform is integrated into attention learning for joint low-light enhancement and noise suppression. Particularly, the proposed wavelet-based attention network includes a Decomposition-Net, an Enhancement-Net and a Restoration-Net. In Decomposition-Net, to benefit denoising, wavelet transform layers are designed for separating noise and global content information into different frequency features. Furthermore, an attention-based strategy is introduced to progressively select suitable frequency features for accurately restoring illumination and reflectance according to Retinex theory. In addition, Enhancement-Net is introduced for further removing degradations in reflectance and adjusting illumination, while Restoration-Net employs conditional adversarial learning to adversarially improve the visual quality of final restored results based on enhanced illumination and reflectance. Extensive experiments on several public datasets demonstrate that the proposed method achieves more pleasing results than state-of-the-art methods.