论文标题

透过嘈杂的黑暗看:迈向现实世界的低光图像增强和降解

Seeing Through the Noisy Dark: Towards Real-world Low-Light Image Enhancement and Denoising

论文作者

Ren, Jiahuan, Zhang, Zhao, Hong, Richang, Xu, Mingliang, Yang, Yi, Yan, Shuicheng

论文摘要

低光图像增强(LLIE)旨在通过照明噪声来改善黑暗图像的照明和可见性。为了处理经常具有沉重且复杂的噪音的实际低光图像,已经为关节和DeNoising付出了一些努力,但是,这只能够实现较低的恢复性能。我们将其归因于两个挑战:1)在现实世界中低光的图像中,噪声在某种程度上被低光覆盖,而在增强过程中不可避免地会放大降解后的左噪声; 2)将原始数据转换为SRGB会导致信息丢失,也会导致更多的噪声,因此,先前在原始数据上训练的LLIE方法不适合更常见的SRGB图像。在这项工作中,我们提出了一个新型的低光增强和DeNoising网络,用于SRGB颜色空间中现实世界中低光图像(RLED-NET)。在RLED-NET中,我们应用插件可区分的潜在子空间重建块(LSRB)将现实世界图像嵌入到低级别子空间中以抑制噪声并纠正误差,以便有效地缩小增强过程中噪声的影响。然后,我们提出了一个有效的交叉通道和移位窗口变压器(CST)层,该层具有两个分支,以计算窗口和通道的注意,以抵抗由输入图像中噪声引起的降解(例如,斑点噪声和模糊)。基于CST层,我们进一步提出了U型结构网络CSTNET,作为深度功能恢复的骨架,并构建一个特征精炼块以完善最终功能。对真实嘈杂图像和公共图像数据库进行的广泛实验很好地验证了拟建的RLED-NET对RLLIE的有效性,并同时验证了deNO的有效性。

Low-light image enhancement (LLIE) aims at improving the illumination and visibility of dark images with lighting noise. To handle the real-world low-light images often with heavy and complex noise, some efforts have been made for joint LLIE and denoising, which however only achieve inferior restoration performance. We attribute it to two challenges: 1) in real-world low-light images, noise is somewhat covered by low-lighting and the left noise after denoising would be inevitably amplified during enhancement; 2) conversion of raw data to sRGB would cause information loss and also more noise, and hence prior LLIE methods trained on raw data are unsuitable for more common sRGB images. In this work, we propose a novel Low-light Enhancement & Denoising Network for real-world low-light images (RLED-Net) in the sRGB color space. In RLED-Net, we apply a plug-and-play differentiable Latent Subspace Reconstruction Block (LSRB) to embed the real-world images into low-rank subspaces to suppress the noise and rectify the errors, such that the impact of noise during enhancement can be effectively shrunk. We then present an efficient Crossed-channel & Shift-window Transformer (CST) layer with two branches to calculate the window and channel attentions to resist the degradation (e.g., speckle noise and blur) caused by the noise in input images. Based on the CST layers, we further present a U-structure network CSTNet as backbone for deep feature recovery, and construct a feature refine block to refine the final features. Extensive experiments on both real noisy images and public image databases well verify the effectiveness of the proposed RLED-Net for RLLIE and denoising simultaneously.

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