| US 7,518,753 B2 | ||
| Full control multilevel error diffusion | ||
| Koen Vande Velde, Duffel (Belgium) | ||
| Assigned to Agfa Graphics NV, Mortsel (Belgium) | ||
| Filed on May 20, 2005, as Appl. No. 11/133,994. | ||
| Claims priority of provisional application 60/572834, filed on May 20, 2004. | ||
| Prior Publication US 2005/0270583 A1, Dec. 08, 2005 | ||
| Int. Cl. G06K 15/00 (2006.01) | ||
| U.S. Cl. 358—3.03 [358/3.02; 358/3.04; 358/1.9; 382/162; 347/15; 400/76] | 11 Claims |
| 1. 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.
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