Local Covariance Filtering for Color Images

In this paper, we introduce a novel edge-aware filter that manipulates the local covariances of a color image. A covariance matrix obtained at each pixel is decomposed by the singular value decomposition (SVD), then diagonal eigenvalues are filtered by characteristic control functions. Our filter form generalizes a wide class of edge-aware filters. Once the SVDs are calculated, users can control the filter characteristic graphically by modifying the curve of the characteristic control functions, just like tone curve manipulation while seeing a result in real-time. We also introduce an efficient iterative calculation of the pixel-wise SVD which is able to significantly reduce its execution time.