| 摘要 |
PURPOSE:To obtain a clear binary picture even from character lines of low contrast by judging background flatness and aimed density difference collectively for each opposite directions and binary coding judging whether it is character line or not. CONSTITUTION:Aimed subwindows are made around an aimed picture element and pair of surrounding subwindows facing four directions (horizontal, vertical and two oblique directions) of the aimed subwindow are constituted, and character lines are judged from density difference, and background flatness determined from background density difference which is the difference of average density value and background density value and aimed density difference which is the difference of aimed density value and average density value. Thereby, wide density irregularity and lateral shear can be distinguished from character lines, and a binary picture image not influenced by such irregularity and stains can be extracted. Character lines are distinguished from relation between the surrounding subwindows and aimed subwindow. Accordingly, character lines can be extracted and binarized even when there is gentle change of background of period wider than the width of tetragonal lattice window.
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