| 摘要 |
For detecting tampering made on a paper document, by carrying out image processing on grayscale image data optically read from the paper document, amplifying a predetermined grayscale value on the grayscale image data, and also, reducing the other grayscale values; and detecting whether or not the paper document has been tampered, according to grayscale converted data calculated based on first grayscale image data obtained from reading an obverse side of the paper document and second grayscale image data obtained from reading a reverse side of the paper document.
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