Patent ID: 7518753

Claim:
A method for processing a digitized continuous tone image for reproducing the image by a printing device, the image including a plurality of input pixels having pixel tone values, wherein for each input pixel the printing device renders a corresponding output pixel by printing a level out of a plurality of available levels defined by a combination of a dot size and dot density or an overlap of dot size and dot density, including a level for printing no dot, the method comprising the steps of: a) defining for each of the available levels a levelsplit curve, each levelsplit curve defining over the range of input pixel tone values an average contribution of the level for rendering that input pixel tone value; b) inputting a tone value of an input pixel of the image; c) applying the levelsplit curves to the tone value for obtaining the average contributions for each of the available levels; d) modifying the average contributions by adding to them diffused quantization errors obtained from a previous processing step to obtain modified average contributions; e) calculating the sum of the modified average contributions; f) if the sum does not exceed a threshold, selecting for the output pixel the level that corresponds to printing no dot; g) if the sum does exceed the threshold, determining which of the modified average contributions has the greatest value, and selecting for the output pixel the corresponding level; h) determining a quantization error between the modified average contributions and the contribution of the selected level; i) diffusing the quantization error to the average contribution of at least one unprocessed input pixel; j) printing the output pixels.