| 摘要 |
The present invention is a method and apparatus for printing documents such as checks that includes an almost imperceptible security image or string of characters on the original face of the document. However, a scanned image of the original document (such as a photocopy) includes a clearly visible presentation of the security image or string of characters that distinguishes the photocopy from the original. The method of creating the security image involves printing a background of a gray scale, removing a portion of the gray scale in the shape of a security image or text, and printing a second gray scale in the removed area causing the two gray scales to appear as one, but where a scanned image of the document distinguishes the two gray scales to reveal the security image.
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