| 摘要 |
PURPOSE:To apply the gradation processing to any type of pictures by detecting accurately the degree of incongruity to the gradation processing, and varying the phase correction amount of a dither matrix in response to said degree of incongruence. CONSTITUTION:The density difference 9 is compared with the fixed threshold value 41 by a comparator 40. The comparator 40 also delivers a signal accordant with the difference to a signal line 42. The threshold values 1-n are decided from the distribution of density differences that is estimated by the different fixed threshold values. The comparators 51-54 delivers '1' when the difference 9 is larger than the threshold value (i) (i=1-n). A parallel/serial conversion part 55 produces pluses to the line 42 in the number equal to the number of comparators having the output '1' respectively among those comparators 51-54. Then the phase change amount 47 (either one of 0, k1-kn) of a dither matrix equivalent to the density difference is decided. The dither processing is given to the next block by the dither matrix whose phase is changed. As a result, the cyclic property is broken for generation of the dither matrix. In such a way the generation of moire is suppressed.
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