| 摘要 |
PURPOSE:To attain binary-coding without missing of contrast picture information at each part even if there exists density gradient in a contrast picture by dividing the contrast picture into plural small regions, calculating histogram at each divided region and obtaining a threshold value of binary-coding. CONSTITUTION:The contrast picture is stored in an input memory 1 and the entire content of the input memory 1 is transmitted to a histogram operator 2 through a data line (a) and the entire histogram is calculated at the device 2. A threshold value deciding circuit 3 inputs the histogram obtained at the histogram operator 2 via a data line (b) to decide the threshold value for binary- coding. On the other hand, the histogram obtained by the histogram operator 2 is fed to a threshold width deciding circuit 4 via a data line (c) and the threshold width is decided by referencing the threshold value data line (d) binary-coded from the entire picture being an output of the threshold value deciding circuit 3. Threshold value deciding circuits 6a, 6b,-,6n decide the threshold value for binary-coding in each small region based on the content obtained via data lines f1, f2,-,fn.
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