| 摘要 |
PURPOSE:To effectively detect a feature and to improve a reliability of a system by providing a gain control means for controlling variable density threshold according to a black line length or a white line length on respective scanning lines in a picture. CONSTITUTION:A picture input part 21 supplies the variable density value of a picture element on the respective scanning lines of the stored various density picture to a binarization part 22, the variable density value of the picture element is compared with a prescribed variable density threshold to perform the binarization of the picture element and fed to an AGC part 24. In the AGC part 24, the black line length or the white line length on the binarization scanning line is obtained, and compared with a previously stored line length threshold. When the black line length or the white line length is larger than the line length threshold, the variable density threshold is subtracted by a previously stored fixed value in the binarization part 22 and the picture element producing the respective line length is binarized again. A coordinate means 23 coordinates two-dimensionally based on a position relation of the black line or the white line on the respective scanning lines obtained by the binarization and the black line or the white line on the adjacent scanning line.
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