Block-based histogram packing of color-quantized images
ICME '03 Proceedings of the 2003 International Conference on Multimedia and Expo - Volume 2
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Abstract: The efficiency of lossless compression algorithms for fixed palette images (also called indexed images) changes if a different indexing scheme is adopted. Indeed, these algorithms adopt a differential-predictive approach of some sort: if the spatial distribution of the indexes over the image is smooth, greater compression ratios may be obtained. It becomes hence relevant to find an indexing scheme that realizes such a smooth distribution. This seems to be a hard problem and only approximate answers can be provided if realistic run-time has to be achieved. In this paper we propose a new indexing scheme, based on an approximate algorithm that maximizes the cost of a Hamiltonian path in a weighted graph. The proposed technique compares favourably with the algorithm proposed by Zeng et al. in [7]. The computational complexity of the two algorithms is compared and experimental tests that show relative compression rates are reported.