| 摘要 |
PURPOSE:To improve the resolution of a binary image and to automatically identify a binary image from a half-tone image such as a photograph by deciding such a reference picture element that the density difference between itself and an attended picture element is larger than a prescribed value to a white or black edge, then outputting a white or a black pattern to a binarization processing part. CONSTITUTION:In a pre-processing part 13, the presence/absence of an edger detection is decided depending on the density difference: i( i=Pi-Px) between an attended picture element Px and a reference picture element Pi (i=1-8). If the absolute value of the difference i is smaller than an edge detection threshold TH1 (TH1>0), the absence of edge detection is decided on, and the attended picture element Px is held in an output picture element data Px'; if larger, an edge detection is decided to be present, and a white or a black edge is decided on to be. That is, if a relation i<=-TH1 is satisfied against the reference picture element Pi, a white edge is decided, but if i<=TH1 is satisfied, a black edge is decided, and a white or a black data is respectively held in an output picture element data Px'. Thus obtained output picture element data Px' is outputted as a picture element data to the binary processing part 14 in the latter stage.
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