Spread-Spectrum Watermark by Synthesizing Texture
Image watermarking is a mapping from watermark message to a set of image counterparts, where every version conveys the same meaning with the original image. Since textures that present single perceptual meaning have certain diversity, an intuitive idea of
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Abstract. Image watermarking is a mapping from watermark message to a set of image counterparts, where every version conveys the same meaning with the original image. Since textures that present single perceptual meaning have certain diversity, an intuitive idea of watermarking is to replace the texture region of an image with a similar-looking synthetic texture containing the watermark. We propose a spread-spectrum watermarking scheme by integrating existent work on texture extraction, segmentation and synthesis, and obtain suggestive results, including (1) the synthetic watermarks can resist adaptive Wiener filtering attack due to its power spectrum similar with the original image; (2) if using the spread-spectrum carrier which is designed elaborately according to the subspace spanned by the textures, hiding capacity can be improved by 20%, while effective hiding capacity under Wiener filtering attack can be doubled; (3) the proposed watermarking scheme also enlighten a sophisticate strategy for watermark attack.
1 Introduction Watermarking, also called steganography, is to discreetly embed information into media signals without eliciting noticeable distortion. For the applications which do not demand strict media fidelity, such as covert communication or rights management for entertainment media, unnoticeablity of distortion is reasonable to be ruled as no changing or confusing the perceptual meaning of the media. In this way, image watermarking is a mapping from watermark message to a set of image counterparts, where every counterpart conveys the same meaning with the original image. In his tutorial literature on data-hiding codes [1], Moulin suggested an idea of connecting image modeling and image watermarking: “A sophisticated embedder or attacker could replace a textured portion of an image (say a grass field) with a similar-looking synthetic texture, introducing negligible perceptual degradation.” To realize the idea, this paper designs a watermarking-by-synthesizing scheme, which integrates existent work of texture extracting, segmenting and synthesizing. Recent work of Balakrishnan [8] propose a image representation method called Hybrid ICA-Mixture of PPCA Algorithm (HIMPA), which use an independent component analysis (ICA) model for edge representation followed by a mixture of probabilistic principal components analyzers (MPPCA) for surface representation. We use a variant of HIMPA for texture extraction and segmentation. A number of texture synthetic algorithms [3] create texture by clever resampling from the original texture. Although the results are visually stunning, they do not H.H.S. Ip et al. (Eds.): PCM 2007, LNCS 4810, pp. 347–356, 2007. © Springer-Verlag Berlin Heidelberg 2007
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W. Liu, F. Zhang, and C. Liu
provide an explicit model for texture and their cooperation with watermarking seem unsystematic, e.g., the method in [4], known as texture block coding, which inserts a textured patch into an area of the image with the same appearance. Founded on certain texture model, some texture sy
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