抑制SAR图像相干斑的迭代方向滤波算法

为保护SAR图像边缘特征并有效提高对乘性相干斑噪声的抑制性能，该文提出一种基于迭代方向滤波的抑制图像相干斑新算法。该算法先借助高斯-伽马平行窗估计出的比率边缘强度映射(ESM)与方向信息，自适应地控制各向异性高斯核(AGK)，生成沿ESM方向分布的具有各向异性支撑区域的局域窗。然后将SAR图像多种局部统计参量联合作为衰减因子，形成与SAR图像区域分布特性相适应的负指数衰减型加权系数，进而将负指数衰减型加权系数与局域窗带方向的各向异性支撑区域结合形成局域加权的方向滤波。最后对SAR图像迭代地进行方向滤波即可实现带边缘保护的相干斑抑制。实验结果表明，与多种抑斑算法相比，该文算法在SAR图像抑斑与边缘保护方面均获得了更好的性能。

SAR Image Despeckling Algorithm Based on Iterative Direction Filtering

In order to preserve the SAR image edge characteristics and improve the suppression performance of multiplicative speckle noise in SAR image, a new despeckling algorithm based on iterative direction filtering is proposed. Firstly, the ratio Edge Strength Map (ESM) and direction information are estimated by Gaussian-Gamma-shaped bi-windows, and anisotropic support domain along the ESM direction is obtained with the ESM and direction information to adaptively control the Anisotropic Gaussian Kernel (AGK) in rectangular local window. Secondly, the decay factor is obtained by combining several local statistics, and the negative-exponential weighting coefficients are produced by the decay factor and are adaptive to the characteristics of regional distribution of SAR image. Thirdly, direction filtering is formed by combining the negative-exponential weighting coefficients and the local window with anisotropic support domain and different directions. Finally, speckle suppression in SAR image with edge protection can be realized by iterative operation of direction filtering. The experimental results show that, compared with most existing despeckling algorithms, the proposed algorithm achieves better performance in the speckle suppression and image edge preservation.