Most deraining methods work on day scenes while leaving nighttime deraining underexplored, where darkness and non-uniform illuminations pose additional challenges. Consequently, night rain has a quite different appearance varying by location and cannot be effectively handled. To accommodate this issue, we propose a Rain Location Prior (RLP) by implicitly learning it from rainy images to reflect rain location information and boost the performance of deraining models by prior injection. Then, we introduce a Rain Prior Injection Module (RPIM) with a multi-scale scheme to modulate it by attention and emphasize the features of rain streak areas for better injection efficiency. Finally, to alleviate the data scarcity issue and facilitate the research on nighttime deraining, we propose the GTAV-NightRain dataset by considering the interaction between rain streaks and non-uniform illuminations, and provide detailed instructions on data collection pipeline which is highly replicable and flexible to integrate challenging factors of rainy night in the future. Our method outperforms state-of-the-art backbone by 1.3 dB in PSNR and generalizes better on real data such as heavy rain and the presence of glow and glaring lights. Ablation studies are conducted to validate the effectiveness of each component and we visualize RLP to show good interpretability. Moreover, we apply our method to daytime deraining and desnow to show good generalizability on other location-dependent degradations. Our method is a step forward in nighttime deraining and the GTAV-NightRain dataset may become a good complement to previous datasets.

Monocular depth estimation has experienced significant progress on terrestrial images in recent years thanks to deep learning advancements. But it remains inadequate for underwater scenes primarily due to data scarcity. Given the inherent challenges of light attenuation and backscat-ter in water, acquiring clear underwater images or precise depth is notably difficult and costly. To mitigate this issue, learning-based approaches often rely on synthetic data or turn to self- or unsupervised manners. Nonetheless, their performance is often hindered by domain gap and looser constraints. In this paper, we propose a novel pipeline for generating photorealistic underwater images using accurate terrestrial depth. This approach facilitates the supervised training of models for underwater depth estimation, effectively reducing the performance disparity between ter-restrial and underwater environments. Contrary to previous synthetic datasets that merely apply style transfer to terres-trial images without scene content change, our approach uniquely creates vivid non-existent underwater scenes by leveraging terrestrial depth data through the innovative Stable Diffusion model. Specifically, we introduce a specialized Depth2Underwater ControlNet, trained on prepared {Underwater, Depth, Text} data triplets, for this generation task. Our newly developed dataset, Atlantis, enables terres-trial depth estimation models to achieve considerable improvements on unseen underwater scenes, surpassing their terrestrial pretrained counterparts both quantitatively and qualitatively. Moreover, we further show its practical utility by applying the improved depth in underwater image enhancement, and its smaller domain gap from the LLVM perspective. Code and dataset are publicly available at https://github.com/zkawfanx/Atlantis.

Rain can significantly degrade image quality and visibility, making deraining a critical area of research in computer vision. Despite recent progress in learning-based deraining methods, there is a lack of focus on nighttime deraining due to the unique challenges posed by non-uniform local illuminations from artificial light sources. Rain streaks in these scenes have diverse appearances that are tightly related to their relative positions to light sources, making it difficult for existing deraining methods to effectively handle them. In this paper, we highlight the importance of rain streak location information in nighttime deraining. Specifically, we propose a Rain Location Prior (RLP) that is learned implicitly from rainy images using a recurrent residual model. This learned prior contains location information of rain streaks and, when injected into deraining models, can significantly improve their performance. To further improve the effectiveness of the learned prior, we also propose a Rain Prior Injection Module (RPIM) to modulate the prior before injection, increasing the importance of features within rain streak areas. Experimental results demonstrate that our approach outperforms existing state-of-the-art methods by about 1dB and effectively improves the performance of deraining models. We also evaluate our method on real night rainy images to show the capability to handle real scenes with fully synthetic data for training. Our method represents a significant step forward in the area of nighttime deraining and highlights the importance of location information in this challenging problem. The code is publicly available at https://github.com/zkawfanx/RLP.

Single image low light enhancement is an important task and it has many practical applications. Most existing methods adopt a single image approach. Although their performance is satisfying on a static single image, we found, however, they suffer serious temporal instability when handling low light videos. We notice the problem is because existing data-driven methods are trained from single image pairs where no temporal information is available. Unfortunately, training from real temporally consistent data is also problematic because it is impossible to collect pixel-wisely paired low and normal light videos under controlled environments in large scale and diversities with noise of identical statistics. In this paper, we propose a novel method to enforce the temporal stability in low light video enhancement with only static images. The key idea is to learn and infer motion field (optical flow) from a single image and synthesize short range video sequences. Our strategy is general and can extend to large scale datasets directly. Based on this idea, we propose our method which can infer motion prior for single image low light video enhancement and enforce temporal consistency. Rigorous experiments and user study demonstrate the state-of-the-art performance of our proposed method. Our code and model will be publicly available at https://github.com/zkawfanx/StableLLVE.