| 摘要 |
<P>PROBLEM TO BE SOLVED: To provide a technology which with a simple structure, achieves highly accurate shading correction regardless of presence of a stain on a reference plate. Ž<P>SOLUTION: A reading-target area on a white reference plate is divided into a plurality of unit segments in a main scan direction, and the unit segment is divided into a plurality of unit regions in a subscan direction; brightness values are obtained by reading each unit region; an average value of the brightness values read from a plurality of unit regions of each group region is calculated for each of a plurality of group regions composed of the plurality of unit regions; the maximum value of the average values calculated for each of the plurality of group regions arranged in the subscan direction corresponding to an arbitrary unit segment in the main scan direction is calculated as the maximum brightness value in the unit segment; and for each unit segment in the main scan direction, it is determined that a stain is present in a group region in which the difference between the calculated average value and the calculated maximum brightness value is larger than a predetermined threshold. Ž<P>COPYRIGHT: (C)2010,JPO&INPIT Ž
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