Fast JPEG Encoding for Color Fax Using HVQ

We derive a JPEG compliant image compressor which is based on hierarchical vector quantization (HVQ). The goal is to reduce complexity while increasing compression speed. For each block, the DCT DC coefficient is encoded in the regular way while the residual is mapped through HVQ to a pre-computed bit-stream corresponding to the compressed DCT AC coefficients. Approximation quality is generally good for high compression ratios. Color Fax is the primary application target for the proposed system.