Reducing granularity in highlights and yellow fields by plane-dependent tables, in device-state error diffusion
 Incremental printing apparatus preferably includes a system for steering the error-diffusion system to respond, to a near-gray or near-yellow input color, with a preselection of a color toward one color plane or toward another color plane. This is not a threshold system. Preferably the steering system operates toward one of the color planes depending on which plane is closer to an input color signal (which includes accumulated error from pixels processed previously, as well as the original signal for a pixel being processed). Preferably the apparatus essentially forecloses use of different inks in adjacent pixels, as distinguished from only modifying a likelihood of using different inks. Preferably the system operates in particular portions of color space that are near a yellow axis. Preferably the two color planes are a cyan and a magenta plane. Preferably the system minimizes granularity in highlight or near-yellow regions of a printed image by causing cyan colorant and magenta colorant in highlight or near-yellow regions to be deposited exclusively remote from one another. Preferably the steering system include portions of a lookup table, and the minimization is effected by contours (preferably diagonal) of permitted cyan and magenta colorant deposition within the table. The invention also includes a method of preparing the table. 
Hewlett-Packard Company
H B
H04N B41J
inventional inventional
Francis E Guo
Bockman Li