Fast VQ codebook search algorithm for grayscale image coding

In this paper, a fast codebook search algorithm that is equivalent to the full search algorithm for image vector quantization is proposed. The image encoding procedure of VQ needs to find the closest codewords in the codebook for image blocks. A great deal of computational cost is consumed in the image encoding procedure. The proposed algorithm employs two test conditions to speedup the image encoding procedure without incurring any extra image distortion. According to the results, an average 95.23% reduction of execution time can be achieved when the codebook of 256 codewords is used in the proposed algorithm.