基于全变分Retinex及梯度域雾天图像增强算法

为提高雾天图像增强的对比度并保持颜色恒常性，提出了基于全变分Retinex及梯度域雾天图像增强算法。首先，采用高斯—赛德尔GS（Gauss-Seidel）迭代算法对基于Retinex的全变分能量泛函数进行求解，从而有效地保持颜色恒常性；其次，采用相对梯度与绝对梯度相结合的方式拉伸雾天图像较亮处的梯度, 在全变分Retinex理论下重建增强后的雾天图像，并将该增强算法应用到彩色图像；最后，加权融合基于全变分Retinex增强算法与梯度域增强算法的增强结果，使得增强结果既能提高对比度又能保持色彩恒常性。实验结果表明,本算法提高了雾天图像增强后的对比度和清晰度，具有颜色恒常性、颜色保真高等特性。

Algorithm for foggy image enhancement based on the total variational Retinex and gradient domain

Considering the preservation of color constancy and the improvement of contrast ratio of foggy image en-hancement, the foggy image enhancement algorithm based on the total variational Retinex gradient domain method was proposed. Firstly, the algorithm used the GS（Gauss-Seidel）iterative method to resolve the Retinex variational energy functional so that the color constancy was remained and the operational velocity of the proposed algorithm was improved. Secondly, the algorithm stretched strongly the gradient of the higher light blocks in the foggy image by combining the relative gradient and the absolute gradient, and reconstructed the foggy enhancement images with the context of least squares and extended the enhancement method to process the color images. Lastly, the enhancement images by using the total variational Retinex method and the gradient domain algorithm were fused weightedly to keep the color constancy and improve the contrast ratio. The experimental results show that the proposed algorithm can effectively improve the image's contrast and definition,the algorithm could keep better color constancy and high color fidelity.