| 摘要 |
PURPOSE:To set a binarization threshold which does not deteriorate the quality of a read picture by counting a picture signal which is binarized according to the binarization threshold, determined based on the picture signal, and changing the binarization threshold according to a count value. CONSTITUTION:A picture density histogram is obtained from a multilevel picture signal 6 by a CPU 20 by a maximum and a minimum detection circuits 21, 22. The peak value of a picture information 6 and the peak value of a white level are obtained from this, and the intermediate density of them is inputted to a comparator 1 as a slice level 7. The comparator 1 compares the signal 6 and the slice level 7, and outputs a binarization signal 8, and a binarization signal counter 2 counts it. The count value 9 is inputted to the comparators 3, 4, and compared with optimum count values C1, C2, and when the value 9 is larger than C1, and when the value 9 is smaller than C2, the outputs 12, 13 of logical 1 are inputted to an AND gate 5, and a picture optimum signal is outputted from an output terminal 14. When the output signals 12, 13 of the comparators 3, 4 are 0, the slice levels C1, C2 are set again.
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