Spherical Coding Algorithm for Wavelet Image Compression
Ateş, Hasan Fehmi
Orchard, Michael T.
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In recent literature, there exist many high-performance wavelet coders that use different spatially adaptive coding techniques in order to exploit the spatial energy compaction property of the wavelet transform. Two crucial issues in adaptive methods are the level of flexibility and the coding efficiency achieved while modeling different image regions and allocating bitrate within the wavelet subbands. In this paper, we introduce the "spherical coder," which provides a new adaptive framework for handling these issues in a simple and effective manner. The coder uses local energy as a direct measure to differentiate between parts of the wavelet subband and to decide how to allocate the available bitrate. As local energy becomes available at finer resolutions, i.e., in smaller size windows, the coder automatically updates its decisions about how to spend the bitrate. We use a hierarchical set of variables to specify and code the local energy up to the highest resolution, i.e., the energy of individual wavelet coefficients. The overall scheme is nonredundant, meaning that the subband information is conveyed using this equivalent set of variables without the need for any side parameters. Despite its simplicity, the algorithm produces PSNR results that are competitive with the state-of-art coders in literature.
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Ateş, Hasan Fehmi; Orchard, Michael T. (IEEE, 2005)In this paper, we introduce the "spherical representation", which provides a new adaptive framework for modeling and coding the image information in wavelet subbands. Based on this representation, a practical coding algorithm ...
Ateş, Hasan Fehmi; Tamer, Engin (IEEE, 2008)In this paper, we present an adaptation of the spherical coder, which has been developed for wavelet transform, to wavelet packets. This coder uses local energy as a direct measure to differentiate the spatial informatin ...
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