| 摘要 |
PURPOSE:To attain proper binarization without causing a phase delay in a threshold signal by applying a convolution operation to a digital picture signal. CONSTITUTION:A 2-dimensional FIR low pass filter 12 applies the convolution operation to a noticed picture element P and 8 referenced picture elements Q,...,W, X therearound and applies the lower pass filter processing in both main scanning and sub scanning directions to calculate a mean operation value VL. An arithmetic means 14 fetches a fixed threshold signal Va from a fixed threshold signal setting means 13 to calculate a variable threshold signal VS based on the mean arithmetic value VL while referencing the fixed threshold value signal Va. On the other hand, a comparator 15 applies binarization processing to a digital picture signal VIN fetched before according to the variable threshold signal VS and gives the obtained binarization signal VOUT to a digital signal output means 16. Thus, the picture signal is binarized without causing the phase delay in the threshold value signal while taking the picture signal change in both main scanning and sub scanning directions properly into consideration.
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