可控核函数的双边滤波算法

为了在滤波时保留更多的图像边缘特征,同时避免现有双边滤波需要人工预设滤波参数的不足,提出了一种参数局部自适应取值的可控核双边滤波算法。构建了适合结构张量和目标尺度描述的可控核函数,并通过结构张量控制可控核函数的方向角和长短轴比例。由目标尺度计算可控核函数的短轴尺度,解决了可控核函数的参数取值问题。使可控核函数投影在图像平滑区域为大尺度圆形,在图像边缘区域为沿边缘方向的细长椭圆形,在角点区域为小尺度圆形。仿真试验结果表明:自适应参数取值的可控核双边滤波在有效滤除噪声的同时能够保留更多的边缘特征,无论是主观评价还是客观评价,本文算法都优于传统双边滤波、对数核函数双边滤波以及改进的双边滤波算法。

Algorithm of steering kernel bilateral filtering

In order to keep edge character and avoid manual pre-definition of the parameters of existing bilateral filtering,a steering kernel bilateral filtering is proposed,which set the parameters of steering kernel adaptively.The steering kernel is designed based on the structure tensor and object scale.The direction angle and the proportion of axial length are set by structure tensor,and the length of short axis is obtained by calculating the object scale.Hence,the projection of the steering kernel is a large-scale circle in smooth regions;it is a slender oval in edge regions,and it changes to small-scale circle in corner regions.Simulation results show that the bilateral filtering based on the steering kernel can filter out the noise effectively and keep more edge characters.The algorithm is superior to traditional bilateral filter,gray-natural logarithm bilateral and the modified bilateral filters in both subjective and objective evaluations.