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基于Retinex理论的解耦级联去噪低光图像增强方法

Low-light image enhancement method based on Retinex theory with decoupled cascaded denoising

  • 摘要: 在低光照的煤矿井下场景中,采集图像一般存在亮度不足、对比度低和噪声干扰等问题,这些因素严重影响了图像质量及后续视觉处理任务的准确性。传统的低照度图像增强算法在复杂环境下易表现出图像失真、过曝、对比度低等问题,而基于无监督学习的算法在优化过程中没有准确的监督信号,导致低光图像在细节恢复与颜色还原方面的增强效果不如有监督学习算法精确。为了解决这一问题,提出一种有监督的新型解耦级联去噪网络。该网络基于HVI色彩空间,将图像的光照强度和色彩信息有效分离,并通过对色彩信息分量进行线性变换,以规避非线性激活函数对负值特征的抑制。其次,根据改进的Retinex理论将低光图像增强时的扰动解耦为由光照估计误差导致的影响图像亮度均衡的过曝、欠曝扰动,以及由反射分量噪声导致的影响图像色彩准确的模糊、伪影扰动,并分别设计了2个U-Net结构的专用去噪器消除上述2条解耦分支中的扰动噪声。其中,去噪器L用于拟合光照分支扰动的逆矩阵,去噪器R用于拟合暗光反射分支扰动的负矩阵,以增强低光图像的自然亮度和色彩表现。此外,为进一步提升性能,设计了一种高效的带有KAN(Kolmogorov-Arnold Network)网络的Linear Transformer模块作为去噪器的核心,该设计通过引入分组参数共享策略和有理多项式函数替代传统Transformer架构中的MLP层,确保网络具有良好非线性拟合能力的同时,能够有效减少参数量,大幅提升模型的表达能力与计算效率。试验结果表明,所提算法在LOL公开数据集与煤矿井下数据集上均取得了最佳性能,同时,在煤矿井下场景的Zero-shot测试任务中展现出显著的泛化性。

     

    Abstract: In low-light coal mine underground scenarios, captured images typically exhibit issues, such as insufficient brightness, low contrast, and noise interference, severely degrading image quality and hindering the accuracy of subsequent visual processing tasks. Traditional low-light image enhancement algorithms are prone to show problems like image distortion, over-exposure, and low contrast in complex environments, unsupervised learning methods lack precise guidance signal, leading to suboptimal detail recovery and color restoration compared to supervised approaches. A novel supervised decoupled cascade denoising network is proposed to address this. The network operates in the HVI color space, effectively separating the image illumination intensity and chrominance, and applying linear transformation to the chrominance component to avoid the suppression of negative-value features by nonlinear activation functions. Additionally, the perturbations encountered during low-light image enhancement are decoupled into two types: Overexposure and underexposure disturbances caused by illumination estimation errors that affect the image’s brightness uniformity, and blurring and artifact disturbances caused by noise in the reflectance component that impact the image’s color accuracy based on the improved Retinex theory. And two U-Net specialized denoisers are respectively designed to eliminate the noise in two decoupled branches. Specifically, denoiser L is employed to approximate the inverse matrix of the illumination branch disturbance, while denoiser R is used to approximate the negative matrix of the reflectance branch disturbance, thereby enhancing the natural brightness and color fidelity of low-light images. Furthermore, an efficient Linear Transformer model with KAN network is designed as the core component of the denoisers for boosting performance. By introducing group-wise parameter sharing strategy and rational polynomial functions to replace the conventional MLP layers in the Transformer architecture, this network possesses strong nonlinear fitting capabilities while significantly reducing the parameters, greatly boosting the expressiveness and computational efficiency. Experiments demonstrate that the proposed algorithm achieves SOTA performance on both the public LOL dataset and the coal mine underground dataset, exhibiting remarkable generalization capability in Zero-shot testing tasks within coal mine underground scenes.

     

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