Explicit coherence enhancing filter with spatial adaptive elliptical kernel

The goal of this letter is to provide an elliptical filter to improve image coherence for the task of image smoothing and inpainting. The kernel of this filter is adaptively weighted and its shape is determined by local coherence estimation. The long axis of its ellipse is the same as the coherence direction and we put more weight there to enhance coherence. Compared with the related anisotropic partial differential equations (PDEs) or wavelet shrinkage methods, the proposed filter is extremely simple, instinctive and easy to code. Numerical examples and comparisons illustrate clearly the good performance of the proposed filter.