| 摘要 |
PURPOSE:To attain the stable binary-coding by recognizing the contrast level of a background part and a character part white referencing the contrast of a center picture element and plural peripheral picture elements so as to recognize the change in the contrast level of the center picture element with respect to the average value. CONSTITUTION:The contrast of plural peripheral picture elements at a position parted from a noticed center picture element by a prescribed distance, that is, an output of a memory 13 of a 2-dimension part is referenced, the maximum contrast and the minimum contrast of the center element are recognized and the result is set to a maximum value calculation circuit 141 and a minimum value calculation circuit 142. The mean value between the calculated maximum and minimum values is calculated by a means value calculation circuit 143 and an absolute value difference calculation circuit 144 calculates the absolute difference between the means value and the contrast of the noticed center picture element. A comparison circuit 145 subtracts a prescribed threshold value alphafrom the result and binary-coding is applied depending on the presence of the remaining value.
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