| 摘要 |
PROBLEM TO BE SOLVED: To determine threshold array where low frequency components are not generated in whole gradations in an image output device reproducing gradation by using a threshold. SOLUTION: Dot image data H generated by threshold array 36M where the threshold T to the prescribed gradation is determined. A candidate pixel which is to be blackened is determined. A low frequency component extracting part 445 extract low frequency component data L from density image data Hd whose density corresponding to the output image of an image output device is simulated with respect to the dot image data H. A specified frequency component resolving part 70 resolves extracted low frequency component data L into specified frequency component data B reinforcing the low frequency component, removes a blackened candidate pixel reinforcing the specified frequency component and narrows the candidate pixel. A blackened candidate pixel position which is thus determined is determined to the arranged position of the threshold of next gradation. Thus, threshold array 36M where the low frequency component can be reduced can be generated.
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