Abstract
One of the important applications of digital watermarking technology is copyright protection and ownership identification for digital images. To achieve this goal, robust watermarking has been rapidly developed in the past decade or so. Robust watermarking is designed to survive various non-geometric manipulations such as JPEG compression, additive noise and filtering as well as some geometric distortions such as rotation and scaling. In this chapter, the fundamental concept of digital watermarking, differences between visible and invisible watermarking, blind and non-blind watermark detection schemes, robust, fragile and semi-fragile watermarking algorithms, as well as four important properties for digital watermarking: imperceptibility, robustness, capacity and security will be described. A number of different transforms and algorithms used for robust image watermarking will be reviewed in detail. These include block based Discrete Cosine Transform (DCT), non-block based Discrete Wavelet Transform (DWT) and other state-of-the-art watermarking algorithms operating in the transform domain. In contrast to conventional transform domain methods, a new adaptive robust watermarking algorithm using the non-redundant contourlet transform known as the wavelet-based contourlet transform (WBCT) is presented in this chapter. From experiments, we exploit the energy relations between parent and children coefficients, which are invariant before and after JPEG compression. Results show that even for QF set as low as 10, the percentages of invariant energy relations of all test images were above 75% after JPEG compression. This invariance feature is therefore very useful for robust image watermarking. The results of WBCT also are evaluated and compared with two other DWT based algorithms achieving high degree of robustness against most non-geometrical and geometrical attacks, while maintaining an excellent perceptual invisibility. © 2010 Springer-Verlag Berlin Heidelberg.