| 摘要 |
PURPOSE:To eliminate the effect of dirt of background onto a picture by changing a threshold value for binary-coding through a binary-coding data corresponding to a preceding picture element. CONSTITUTION:A scanner 1 outputs an analog picture element signal AP corresponding to the density at each picture, the signal is converted into a digital signal DP by an A/D converter 2 and stored in a matrix register 3. A correcting value E' subject to MTF correction at an operating device (spatial filter) 4 is compared with a correcting threshold value SL' outputted from an adder 7 by a digital comparator 5 to output a binary-coding data BD. When the correcting value E' is changed, the correcting threshold value SL' is changed into a value adding the inverted value ''1'' of the binary data BD to the threshold value SL' from the step next to the step judged as white data. While a black picture element is detected from the step next to the step where the correcting value E' is judged as black data, since the inverted value of the binary data BD is ''O'', the correction threshold value is made to a value being identical to the threshold value. |
