| 摘要 |
PURPOSE:To increase the compression rate by selecting a dither binary coding circuit or a slice binary coding circuit without passing through a converting circuit at the selection of a file mode. CONSTITUTION:Only when a maximum value is larger than a prescribed value A and a minimum value is smaller than a prescribed value C in addition to an output of a comparator 7, that is, when a high-level output is generated from comparators, 6, 8 binary picture data outputted from a dither binary coding circuit 4 is selected by a multiplexer 10 by bringing an output of an AND gate circuit 9 to a high level. Since no dither processing is given to a black or a white picture by applying discrimination with the maximum value and the minimum value of the density in addition to the density gradient being the conventional image region criterion, the compression rate at NH coding is improved, for example.
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