基于NSCT变换和暗通道先验的水下图像清晰化算法研究

Underwater Images Visibility Enhance Algorithm Based on NSCT Transform and Dark-Channel Prior

为了解决水下图像对比度低、纹理模糊、亮度不均匀等问题,建立了区别于单色大气散射模型的水下成像模型,提出了一种新的水下图像清晰化算法.该算法在通道间相关性很小的lαβ颜色空间进行处理.首先将l通道通过NSCT变换分解,然后对低频子带采用基于暗通道先验理论的方法进行处理,其关键是设计了非均匀照明条件下的光源强度估计方法,而对不同方向的带通子带则采用拉普拉斯算子进行强化,最后通过NSCT反变换和RGB颜色空间转换得到输出图像.采用不同条件下所获得的水下图像作为实验数据,与其他几种典型算法进行比较,结果表明,所提出的算法能较好地同时满足消除亮度不均、提高对比度、锐化目标的目的,具有一定的优越性.

In order to solve the problem of low contrast,texture blurring and illumination uniform in the underwater images,a new visibility enhancement algorithm which is based on the underwater imaging model being different from the monochrome atmospheric scattering model is proposed in this paper.The algorithm works in the lαβcolor space that has little relevance among channels.Firstly,NSCT transform is used to decompose the l channel.And then the low-frequency band is proposed based on the dark channel prior,among which the key is to design a method for estimating the intensity of light sources under non-uniform lighting condition.The directional bandpass subbands are proposed by convolution with Laplace operator.Finally,the output image is obtained through anti-NSCT transform and RGB color space convertion.The experiment using the images captured under different conditons is conducted to compare the performace of the proposed algorithm with other ones.And the results show that the proposed algorithm in this paper has good performance in eliminating nonuniform brigntness,improving contrast and sharpening the targets,and has certain advantages.