Tone dependent color error diffusion
Conventional grayscale error diffusion halftoning produces worms and other objectionable artifacts. Tone dependent error diffusion (Li, P. and Allebach, J.P. Proc. SPIE Color Imaging, vol.4663, p.310-21, 2002) reduces these artifacts by controlling the diffusion of quantization errors based on the input graylevel. Li and Allebach designed error filter weights and thresholds for each (input) graylevel with optimization based on a human visual system (HVS) model. We extend tone dependent error diffusion to color. In color error diffusion, what color to render becomes a major concern in addition to finding optimal dot patterns. We present a visually optimum design approach for input level (tone) dependent error filters (for each color plane). The resulting halftones reduce traditional error diffusion artifacts and achieve greater accuracy in color rendition.