Nonblind and Quasiblind Natural Preserve Transform Watermarking
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Research Article Nonblind and Quasiblind Natural Preserve Transform Watermarking G. Fahmy,1 M. F. Fahmy,2 and U. S. Mohammed2 1 German
University in Cairo (GUC), New Cairo City 11835, Egypt of Electrical Engineering, Assiut University, Assiut 71515, Egypt
2 Department
Correspondence should be addressed to G. Fahmy, [email protected] Received 10 September 2009; Revised 10 December 2009; Accepted 10 March 2010 Academic Editor: Robert W. Ives Copyright © 2010 G. Fahmy et al. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. This paper describes a new image watermarking technique based on the Natural Preserving Transform (NPT). The proposed watermarking scheme uses NPT to encode a gray scale watermarking logo image or text, into a host image at any location. NPT brings a unique feature which is uniformly distributing the logo across the host image in an imperceptible manner. The contribution of this paper lies is presenting two efficient nonblind and quasiblind watermark extraction techniques. In the quasiblind case, the extraction algorithm requires little information about the original image that is already conveyed by the watermarked image. Moreover, the proposed scheme does not introduce visual quality degradation into the host image while still being able to extract a logo with a relatively large amount of data. The performance and robustness of the proposed technique are tested by applying common image-processing operations such as cropping, noise degradation, and compression. A quantitative measure is proposed to objectify performance; under this measure, the proposed technique outperforms most of the recent techniques in most cases. We also implemented the proposed technique on a hardware platform, digital signal processor (DSK 6713). Results are illustrated to show the effectiveness of the proposed technique, in different noisy environments.
1. Introduction With the widespread use of the Internet and the rapid and massive development of multimedia, there is an impending need for efficient and powerfully effective copyright protection techniques. A variety of image watermarking methods have been proposed [1–14], where most of them are based on the spatial domain [1, 2] or the transform domain [3, 4]. However, in recent years [14–16], several image watermarking techniques based on the transform domain have appeared. Digital watermarking schemes are typically classified into three categories. Private watermarking which requires the prior knowledge of the original information and secret keys at the receiver. Semiprivate or semiblind watermarking where the watermark information and secret keys must be available at the receiver. Public or blind watermarking where the receiver must only know the secret keys [14]. The robustness of private watermarking schemes is high to endure signal processing attacks. However, they are not feasible in real
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