| 摘要 |
PURPOSE:To realize a binary coding method with a clear picture output in a picture with intermediate tone and a line drawing such as a character, by splitting an input picture signal into blocks and setting a threshold value at each block. CONSTITUTION:The density distribution of an original is converted into a serial analog electric signal with an input device 10 and digitized at an AD converter 11. In a shading correction circuit 12, uneven sensitivity and illumination is electrically corrected. The output digital signal is given to a one-block delay circuit 13, an n-picture element's share memory 14, and a differential circuit 15. In the memory 14, data of one block is stored and the circuit 15 derives difference of a time series signal to form a differential signal and in a peak value detection circuit 16, the newest maximum and minimum values are stored one after another. A threshold value decision circuit 17 checks the value of the memory 14, obtains the parameter alpha of a dither matrix, calculates the threshold value matrix and compares the data with an original signal from the delay circuit 13 at a comparator 18 and outputs 1, 0. |
