Chinese Journal of Computers   Full Text
Title	A Contourlet-Domain Watermarking Algorithm Against Geometric Attacks Based on Feature Template
Authors	LOU Ou-Jun WANG Zheng-Xuan
Address	(College of Computer Science and Technology, Jilin University, Changchun 130023)
Year	2009
Issue	No.2(308—317)
Abstract &   Background	Abstract Image watermarking resistant to geometric attacks is the hotspot and challenging point in the state-of-the-art research on watermarking.Even an invisible affine transformation can invalidate most existing watermarking algorithms.This paper analyses and discusses the characteristics of Contourlet transform, and on the basis above, proposes a novel Contourlet-domain watermarking algorithm against geometric attacks based on the feature template matching. The proposed algorithm includes four important techniques: (1) Puting coefficients into one group with the same coordinate in each finest directional subband. Then select the coefficient with the richest texture from each group as the coefficient to be embedded watermarking. Therefore, watermarking can be embedded into significant region as well as highly textured region of the host image; (2) For each coefficient of the selected subband, embeding watermarking with different strength adaptively adjusted in terms of the energy of its parent coefficient in the lowest subband, and the texture of its neighborhood coefficients in finer scale.The choice of embedding position and the embedding strategy above effectively guarantee good transparency and maximum robustness of the proposed algorithm; (3) Improving the Harris-Laplace operator, extract the feature points robust to geometric deformation as template from the embedded image using improved Harris-Laplace operator; (4) When detection, using the transformation between corresponding points in feature template to realize resynchronization, and determining existence of watermarking by statistical correlation between host image and watermarking. Experimental results show the proposed algorithm has good transparency and is very robust to common image processing and geometric attacks. Keywords watermarking; Contourlet; feature point; template; geometry attack Background The ease of duplication and dissemination of digitized multimedia challenges violently copyright protection and information security of digital products. Therefore, watermarking techniques become one of the research hotspots in the discipline of multimedia information security. However, most state-of-the-art watermarking algorithms are well robust only to common image processing, while deficient against geometric attacks. Even an invisible affine transformation can invalidate most existing watermarking algorithms. So the primary objective of the research group is to design effective approaches to still image and video watermarking robust to both common image and video processing attacks and geometric attacks. In the paper “Research on Quantization-Based Robust Video Watermarking Technique against Geometrical Attacks” published in Journal of Computer Research and Development, our group proposes an effective video watermarking algorithm. It achieves good transparency and better resistance against RST attacks and excellent robustness to MPEG compression, frame loss, etc.. In this paper, the authors analyze and discuss the characteristics of Contourlet transform. A novel Contourlet domain image watermarking algorithm against geometric attacks is proposed based on the feature template matching.