Customized JPEG compression for grayscale printing

Describes a procedure by which JPEG compression may be customized for grayscale images that are to be compressed, halftoned, and printed. The technique maintains 100% compatibility with the JPEG standard, and is applicable with any halftoning algorithm. The JPEG quantization table is designed using frequency-domain characteristics of the halftoning patterns and the human visual system, and the Huffman tables are optimized for low-rate coding. The authors present experimental results demonstrating that the customized JPEG encoder offers a significant performance advantage over a coder that uses the default quantization and Huffman tables. The results also show that the customized encoder typically achieves rates in the range 0.13-0.25 bits per pixel (image dependent) with practically no visible compression artifacts in the printed images