Recently a filtering method based on side windows has been reported. Although this method has strong ability to preserve edge structure, its ability to smooth textures is weaker than using a full window. In this paper, we propose a scale adaptive side window based bilateral filter (SASWBF). An expanding ratio parameter is designed to control the side window varying to the full window. To adapt the size of spatial kernel at each pixel, the scale of filtering window is estimated using a structure measure. A bilateral filter using Fourier basis is adopted to accelerate the filter processing. The computational complexity of the proposed smoothing filter does not depend on the window size and thus is in almost constant time. Our experimental results demonstrates that the proposed filter performs well.
Due to its simplicity, median filter is a very famous and useful tool in the fields such as image processing and computer graphics. Median filter is mainly for eliminating irrelevant details, especially removing salt-and- pepper noises in image. It has the ability to preserve structural edges compared with box filter and Gaussian filter, however, this ability is very limited. When the radius of filter window becomes larger, the edge-preserving ability also becomes very weak. In this paper, we propose a median-like filter that removes small details including salt-and-pepper noises in image while having stronger edge-preserving ability than classical median filter. The filter computes the output at the observed pixel using 8 sub-windows and a full window. Among these windows, 4 of them are built on the 4 quadrants respectively, other 4 of them are on left, right, top, and bottom half planes. All of these sub-windows contain the observed pixel. Moreover, since medians are computed from histograms, we update column histograms and kernel histograms by simple subtraction and addition operations to accelerate the filtering. The computational complexity of the proposed median-like filter is independent of window size and thus is in constant time. A SSIM (Structural SIMilarity) evaluation demonstrates that the proposed median-like filter performs well.
Filtering image by eliminating irrelevant details as could as possible while preserving structure edge and corner becomes very important in the fields such as image processing and computer vision etc. In this paper, we present an Anisotropic Rolling Filter (ARF) for smoothing image while preserving important structure edge and corner. The proposed filter implements an extended cross bilateral filter, in which the range weights are updated in an iterative manner, while the spatial Gaussian weights are computed in anisotropic directions instead of isotropic directions. The anisotropic directions are computed based on structure tensors which are calculated at each pixel to determine structure orientations. Compared with the original rolling guidance filter, it is found that the proposed anisotropic rolling filter has stronger smoothing and structure preserving ability.