| 摘要 |
PROBLEM TO BE SOLVED: To provide the original size detector that accurately discriminates and detects edges of an original even when there are more or less points read by black pixels such as characters or dust around edges of the original. SOLUTION: A CCD image sensor 16 as an imaging device reads one line of an image on an original 12 placed on an original placing platen 11. Then pixels whose level changes from a black level to a white level are discriminated to be an edge 12a in a main scanning direction P1 of the original 12 when the number of pixels whose level is read to be a black level among several pixels changed from pixels read to have a black level into pixels read to have a white level is smaller than a prescribed number in the read data by a control means. In this case, a criterion of the number of black pixels p1 to discriminate the edge 12a of the original 12 is in a range of 6-25%.
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