Fundamentals of digital image processing
Fundamentals of digital image processing
Spread Spectrum Systems
Performance Improvement of Spread Spectrum Based Image Watermarking Schemes through M-ary Modulation
IH '99 Proceedings of the Third International Workshop on Information Hiding
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Informally speaking, a digital watermark is some usually imperceptible embedded control code carrying information related to the intellectual property rights of the data. When we deal with the application of watermarks in digital imaging an essential requirement is that embedded watermarks can still successfully be detected after an image has been printed out and scanned in again.Printing and scanning causes a number of alterations to the image: A/D and D/A conversion, filtering, modification of resolution on and slight changes in image geometry due to imperfections of devices and personnel involved in the process. Even more, when scanning in a printed image we usually have no idea about the pixel resolution of the original digital image, a significant problem in watermark detection applications.In this contribution we present novel watermark embedding and corresponding detection algorithms that are capable of dealing with these aforementioned difficulties. It can be expected that these findings might be of considerable importance to bring digital watermarking one step closer to practical image copyright enforcement.