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Design of optimized contourlet filters for improved coding gain

The separable wavelet transform has limited directional sensitivity and is suboptimal for compression of textured images. A finer directional resolution and better coding results can be achieved by contourlet transform. So far, directional filters based on design criteria that are unspecific to image compression were used for contourlet transform. We propose directional filters that are optimized specifically for image coding. Thereto, a filter design method that is based on maximization of coding gain was developed. Directional filters were designed for all images of two standard test image databases and compared experimentally to standard filters. In most cases the newly designed filters performed better than standard filters.