Use of space filling curves in fast encoding of VQ images

The use of space filling curves to encode image input blocks in vector quantization (VQ) is proposed. It is based on computing a group of Peano scannings of selected feature vectors for each codeword in the codebook. An ordered list of the Peano scannings and their link to the codebook is stored. Coding is conducted by restricting the search to two windows of codewords with the closest Peano scannings to that of the input block. Each window center is found in logarithmic time proportional to the codebook size. The number of codewords to be searched is fixed and is determined by some additional distortion that is acceptable over exhaustive search methods. Simulation results produced coded images with no significant degradation while maintaining considerable constant search time savings over exhaustive search methods. The algorithm can be used with some other fast full-search equivalent methods as well.