| 摘要 |
An apparatus prohibits an unfair copying of a document by forming a latent image region and a background region on the document in a manner that prevents detection of their existence. The apparatus has a controller that detects background region densities and latent image region densities. The controller extracts only a background region density, which enables a special dot pattern to be detected when copying the image of the document. The controller also extracts only a latent image region density, at which a dot image corresponding to the dots constituting the latent image region is not formed on a copy when copying the image of the document. The controller then derives the background region densities and the latent image region density matching with the background region density.
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