Structural Residual Learning for Single Image Rain Removal
This work improves image processing tasks by enhancing rain removal for practical applications, though it is incremental as it builds on existing CNN-based approaches.
The paper tackles the problem of single image rain removal by addressing the overfitting and poor generalization of existing CNN-based methods to diverse rain streaks. It proposes a structural residual learning network that enforces rain layer extraction to comply with prior knowledge, achieving better training accuracy and testing generalization on synthetic and real datasets compared to state-of-the-art methods.
To alleviate the adverse effect of rain streaks in image processing tasks, CNN-based single image rain removal methods have been recently proposed. However, the performance of these deep learning methods largely relies on the covering range of rain shapes contained in the pre-collected training rainy-clean image pairs. This makes them easily trapped into the overfitting-to-the-training-samples issue and cannot finely generalize to practical rainy images with complex and diverse rain streaks. Against this generalization issue, this study proposes a new network architecture by enforcing the output residual of the network possess intrinsic rain structures. Such a structural residual setting guarantees the rain layer extracted by the network finely comply with the prior knowledge of general rain streaks, and thus regulates sound rain shapes capable of being well extracted from rainy images in both training and predicting stages. Such a general regularization function naturally leads to both its better training accuracy and testing generalization capability even for those non-seen rain configurations. Such superiority is comprehensively substantiated by experiments implemented on synthetic and real datasets both visually and quantitatively as compared with current state-of-the-art methods.