Upper bits separation coding of images using vector quantization

An effective vector quantization technique is described. The image is separated into two images: an upper bit image with two bits and a lower bit image with six bits. The upper bit image is exactly encoded using the run-length coding scheme, while the lower bit image is divided into sub blocks, and then encoded by the vector quantizer. The basic properties of the bits separation are discussed and demonstrated by examples. Experimental results are given, and comparisons between the proposed approach and some other vector quantizers are presented. The reconstructed image quality obtained with bit-separation vector quantization scheme is found to be superior