A. Pramila, A. Keskinarkaus, and T. Seppänen (Finland)
Digital watermark, print-cam process, camera phones, digital camera
In this paper, the possibility to apply conventional watermarking methods in a print-cam process is discussed. In the print-cam process, the watermark is read from a printed image with a camera phone. The process inflicts serious attacks to the watermark and, especially geometrical distortions. If the distortions are not inverted, they may destroy the watermark. In this paper, the distortions are corrected from the captured image with invisible, and visible templates and the message is successfully extracted after the distortions have been corrected. The BER values obtained are beneath 1.1% with resolution of 1600x1200 and JPEG quality factors of 100% and 80%. The success ratios are above 98% with respective settings, which shows that the inversion of the distortions was successful and the watermarking method is robust against the print-cam process.
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