| 摘要 |
PROBLEM TO BE SOLVED: To provide a method, capable of pseudo-gradation processing of high precision by adopting thresholds and output gradation different by each color, even when combining at least two colors and using an error diffusion method. SOLUTION: The method is provided with adders 1-0 and 1-1 for adding respective error values E0 and E1, between each of the multi-valued pixel signal values of plural colors and the pseudo-gradation signal value of the same color and output-deciding parts 2-0 and 2-1 for outputting temporarily decided pseudo gradation signals to the respective output value of adding parts. The method is provided with first error calculation parts 3-0 and 3-1 for outputting an error between each of the temporarily-decided pseudo-gradation signals and an output corresponding to the adding parts, the second output deciding part 2-2 for outputting multicolor pseudo-gradation signals with respect to a color obtained by the plural colors, and output changing parts 4-0 and 4-1 for outputting each of the temporarily decided pseudo-gradation signals by changing or without changing it, based on the deciding result by an output change judging part 4 for deciding the need for changes, concerning each of the temporarily decided pseudo-gradation signals, based on the temporarily-decided pseudo-gradation signals and all outputs of the first error calculation part and the multicolor pseudo-gradation signals.
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