基于中值滤波和偏振调制的雾天偏振图像快速增强方法研究

Research on a fast enhancement method of polarization images in foggy weather based on median filter and polarization modulation

针对现有偏振去雾算法难以兼顾去雾效果和实时性问题,提出了一种基于中值滤波和偏振调制的雾天偏振图像快速增强方法。利用中值滤波估算大气光;采取半反法估计无穷远处大气光强,并基于大气散射模型对图像进行恢复;使用场景偏振度对恢复的图像进行偏振调制增强。相比较其他方法,文章通过降采样方法减少图像尺寸,选取小尺度的滤波窗口,在保持足够的大气光估算精度的同时,显著降低了处理时间,并采用偏振调制和直方图均衡化方法提高目标与背景的对比度,较好地解决了去雾效果和算法实时性问题。实验结果表明,经过该方法增强的图像,在信息熵、去雾前后梯度比、目标与背景对比度等三个指标上都有较大提升,达到了良好的去雾效果;对于分辨率为1393×986的图像,处理时间仅为16ms,完全满足实时性要求。

A fast enhancement method of polarization images in foggy weather based on median filter and polarization modulation is proposed to balance between dehazing effect and real-time processing. Firstly, the median filter method is used to estimate atmospheric light. Secondly, the semi-inverse method is applied to get the atmospheric light intensity at infinity, and the restored image is obtained by using scattering model. Finally, the image is adjusted with the degree of linear polarization to promote visual effect.In comparison with other methods,the downsampling method is used in this paper to reduce the image size.Furthermore,the smaller scale of filter window is chosen to decrease the handling time significantly in the premise of maintaining accuracy of atmospheric light estimation.What's more,Polarization modulation and histogram equalization methods are utilized to improve the contrast ratio between the target and the background,solving the problem of defogging effect and real-time algorithm better.The experiment shows that the results of this method has a great improvement in three metrics,such as entropy,gradient ratio before and after dehazing,and contrast.For image with a resolution of 1393×986,the processing time is only 16ms,which fully meets our real-time requirements.