| 摘要 |
PROBLEM TO BE SOLVED: To fast extract a half-tone dot meshing area in a document image by distinguishing a graphic and photograph area from a half-tone dot meshing area of a character area with high accuracy. SOLUTION: A black run is extracted from the continuity of black pixels in document image data (step S1), and a circumscribed rectangle of the black run is extracted (step S2). In rectangle integration processing, processing for integrating small dots (rectangle) located within a distance (e.g. distance within 15 pixels) within ?a prescribed threshold is performed with horizontal (step S3) or vertical (step S4) threshold processing with respect to an extracted distance between small dots to extract a rectangle as a rectangle of a half-tone dot meshing candidate area. The size of the half-tone dot meshing candidate area is examined from coordinates information of the half-tone dot meshing candidate area generated by the rectangular integration processing to decide whether it is a half-tone dot meshing area (step S5).
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