ERL-Net: Entangled Representation Learning for Single Image De-Raining

Despite the significant progress achieved in image de-raining by training an encoder-decoder network within the image-to-image translation formulation, blurry results with missing details indicate the deficiency of the existing models. By interpreting the de-raining encoder-decoder network as a conditional generator, within which the decoder acts as a generator conditioned on the embedding learned by the encoder, the unsatisfactory output can be attributed to the low-quality embedding learned by the encoder. In this paper, we hypothesize that there exists an inherent mapping between the low-quality embedding to a latent optimal one, with which the generator (decoder) can produce much better results. To improve the de-raining results significantly over existing models, we propose to learn this mapping by formulating a residual learning branch, that is capable of adaptively adding residuals to the original low-quality embedding in a representation entanglement manner. Using an embedding learned this way, the decoder is able to generate much more satisfactory de-raining results with better detail recovery and rain artefacts removal, providing new state-of-the-art results on four benchmark datasets with considerable improvement (i.e., on the challenging Rain100H data, an improvement of 4.19dB on PSNR and 5% on SSIM is obtained). The entanglement can be easily adopted into any encoder-decoder based image restoration networks. Besides, we propose a series of evaluation metrics to investigate the specific contribution of the proposed entangled representation learning mechanism. Codes are available at 〈https://github.com/RobinCSIRO/ERL-Net-for-Single-Image-Deraining〉.