| 摘要 |
PROBLEM TO BE SOLVED: To provide an adaptive illumination correcting device which can eliminate problems such as making the whole surface of a page with a binding part of a book in between in close contact with the platen surface, or detecting the variations in the height of a document. SOLUTION: This device scans such a part as nonplanar origin document as the binding part of a book, generates scanned image data, obtains illumination variation data from the scanned image data, derives a number of illumination compensation values from the obtained illumination variation data, and changes the scanning image data in accordance with the illumination compensation values. Such illumination variation data acquisition includes measurement of illumination values at a number of pixel positions within a sampling window. The illumination compensation deriving step includes the setting of background and foreground illumination distributions for each set of illumination values within the sampling windows, decision of lower background threshold value BL and higher background threshold value BH based on each background distribution respectively, and decision of lower foreground threshold value FL and lower foreground threshold value FH based on each foreground distribution respectively, and also calculation of reference values for BL, BH, FL and FH from a plurality of decided threshold values.
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