Abstract: This paper deals with still image subband coding with adaptive filter banks. Based on an analysis of distortions in coders with fixed filter banks with different characteristics, the scheme with spatially adaptive filter banks is developed. The main objective is to construct a subband coder in which both ringing noise and blocking artifacts are reduced. With respect to local image characteristics, suitable filter responses are selected to achieve this aim. The selection is based on measuring of edge business and edge orientation. A second objective is to reduce border distortions caused by the circular extension method by employing filters with short unit pulse responses in the border regions. It turns out that subband coding with adaptive filter banks in combination with an optimum filter selection strategy achieves a good trade-off between ringing noise and blocking effects. We conclude that the presented scheme for automatic filter selection works well for a large class of images with reasonably high contrast. For 'smooth-looking' images further work to improve the robustness of the algorithm is needed. The use of adaptive filtering in the image border regions solves - to some extent - the distortion problems encountered when using the circular extension method.!13
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