Lossy compression of clustered-dot halftones

We propose a coding algorithm for lossy compression of digital halftones produced by clustered-dot dithering. Our scheme is based on pixel ordering and run-length coding, and has small memory and computation requirements. Data reduction techniques give an efficient, but imperfect, representation of the run lengths, allowing low-rate coding along with a good approximation to the original dot structure. Experiments with 1024×1024 images, 8×8 dithering cells, and 600 dpi printing have shown that the algorithm maintains good image quality while achieving rates of about 0.1 bits per pixel