一种带约束搜索窗的非局部平均相干斑抑制算法  

Non-Local Means Suppression Algorithm of Speckle with Restrained Search Window

作　　者：李敬曼 朱磊[1] 张博[1] 潘杨[1] LI Jingman;ZHU Lei;ZHANG Bo;PAN Yang(College of Electronics and Information,Xi’an Polytechnic University,Xi’an 710048,China)

机构地区：[1]西安工程大学电子信息学院,西安710048

出　　处：《西安交通大学学报》2020年第10期54-62,共9页Journal of Xi'an Jiaotong University

基　　金：国家自然科学基金资助项目(61971339);陕西省重点研发计划资助项目(2019GY-113);西安市科技局创新引导计划资助项目(201805030YD8CG14(6))。

摘　　要：为了提升非局部平均(NLM)滤波对合成孔径雷达(SAR)图像乘性相干斑噪声的抑制性能,提出了一种带约束搜索窗(RSW)的NLM抑斑算法RSW-NLM。首先估计搜索窗内像素灰度分布概率密度函数的极大值,并将极大值对应的像素作为聚类中心;然后利用均值比形成的相似性测量函数对搜索窗内各像素进行聚类划分,进而通过保留中心像素所属聚类,形成一种限制与中心像素相似性偏低的像素参与NLM滤波的带约束搜索窗;最后,在带约束搜索窗内实施由局部均值比和变差系数构建的适应SAR图像乘性相干斑噪声的NLM滤波。实验结果表明,RSW-NLM算法与SAR图像三维块匹配算法、基于变差系数的NLM算法以及基于均值比的NLM算法相比,在充分抑制了相干斑的同时,有效保护了边缘、细节等信息,尤其是灰度值接近的弱边缘,其等效视数提高2%以上,边缘保持指数提高1%以上。A new non-local means(NLM)despeckling algorithm(RSW-NLM)with restrained search window is proposed to improve the performance of NLM filtering for reducing multiplicative speckle noise of synthetic aperture radar(SAR)images.Firstly,the maximums of probability density function of pixel gray distribution in search window are estimated,and the pixels corresponding to the maximums are taken as clustering centers.Secondly,a similarity measurement function formed by the ration of means is used to cluster the pixels in the search window.Then,a restrained search window is formed by keeping the cluster with the central pixel,and pixels with low similarity to the central pixel are restricted from participating in NLM filtering process.Finally,the NLM filter adapting to the multiplicative coherent speckle noise of SAR images constructed by local mean ratio and variation coefficient is implemented in the restrained search window.Experimental result and comparisons with a 3D block matching algorithm of SAR images,a NLM algorithm based on coefficient variation and a NLM algorithm based on mean ratio show that the RSW-NLM algorithm fully suppresses the coherent spots,while effectively protects the information such as edges and details,especially the weak edges with close gray value,and that the equivalent number of looks increases by more than 2%,and the edge preservation index improves by more than 1%.

关 键 词：合成孔径雷达 相干斑抑制 非局部平均 约束搜索窗 

分 类 号：TP751[自动化与计算机技术—检测技术与自动化装置]