【作者】 邬俊；

【导师】 王向阳；

【作者基本信息】 辽宁师范大学 ， 计算机软件与理论， 2007， 硕士

【摘要】 20世纪末的数字革命,特别是计算机网络和多媒体技术的发展,为人类带来了无限的可能与便利,但也使得与之相关的数字作品侵权问题显得越来越严重。作为数字产品版权保护和信息安全维护的一种有效手段,数字水印近年来得到了学术界和商界的广泛关注。它在不影响数字作品(如数字图像、视频、音频等)使用质量的前提下,将一种不可见的标记(水印)内嵌到媒体产品中,以实现对该产品的保护或监控。当前数字水印尚存在很多待解决的问题,其中鲁棒性是诸多关键问题之一。如何设计高度鲁棒性的数字图像水印方案始终是数字水印领域中的一个开放课题。针对鲁棒性数字图像水印技术中的一个难点-同步问题,文本主要做了如下研究工作:1,提出了一种归一化DWT(Discrete Wavelet Transform)域图像水印算法。该算法以图像归一化技术和小波变换为基础,并结合HVS(Human Visual System)的掩蔽特性,在归一化图像重要区域内自适应地嵌入水印信息。实验证明,该水印方案不仅具有较好的透明性,而且对常规信号处理和全局性几何扭曲(包括旋转、缩放、平移、任意仿射变换和镜像翻转等)均具有较好的鲁棒性。2,提出了一种基于自适应特征区域的图像水印算法。该算法以特征点提取技术为基础,同时利用特征尺度理论自适应地确定局部特征区域,然后在每个局部特征区域的DFT(Discrete Fourier Transform)域内独立地嵌入水印信息。实验证明,该水印算法在保证透明性的前提下,不但可有效地抵抗常规信号处理和全局性几何扭曲,还对行列移除、大面积剪切,局部随机弯曲等较复杂的局部几何攻击具有较强抵抗能力。3,提出了一种基于神经网络的半色调数字图像水印算法。该算法充分考虑了数字图像半色调处理的特性,并以神经网络为基础,通过自适应地调节误差扩散核的方式,实现了水印信息的嵌入与半色调处理同时完成。检测时,通过几何校正的方式实现数字水印的重同步。实验证明,该水印算法具有较好的透明性,而且可抵抗常规的信号处理及打印-扫描攻击。更多还原

【Abstract】 In the end of 20’Th century, the digital revolution included computer network and multimedia techniques brings limitless convenience for people. However, the problem about the intellectual property rights has become increasingly serious. As an effective solution to this problem, digital watermarking which embeds an imperceptible signal (watermark) into the multimedia data in order to defeat unauthorized copying and intentional tampering has attracted large numbers of attention in the information security field. Recently, there are many unresolved problems in the digital image watermarking field. The robustness is one of the problems and the watermark synchronization is very crucial to design robust image watermarking scheme. Therefore, how to develop the robust digital image watermarking schemes against de-synchronization attacks has been a key problem in the past years. In this paper, three novel image watermarking schemes are proposed to cope with the de-synchronization attacks.1, a normalization DWT (Discrete Wavelet Transform) domain based image watermarking algorithm has been presented. Based on image normalization and DWT technique, the watermark is adaptively embedded in the DWT domain in accordance with the conceal quality of HVS (Human Visual System). This is a blind watermark algorithm to confirm the copyright without the original image. Experimental results show that the proposed scheme is not only invisible, but also robust against common signals processing and global geometric distortion.2, an adaptive characteristic regions based image watermarking algorithm has been presented. The robust feature points are extracted by using Harris-Laplace detector. Based on the scale-space theory, the adaptive characteristic regions are constructed in accordance with the positions and characteristic scale of the feature points. The watermark is repeatedly embedded into all regions by modulating the magnitudes of DFT coefficients. Experimental results show that the proposed scheme is invisible and robust against common signals processing such as median filtering, sharpening, noise adding, and JPEG compression etc, and de-synchronization attacks such as rotation, scaling, translation (RST), row or column removal, cropping, and random bend attack (RBA) etc.3, a neural network based halftone image-watermarking algorithm has been presented. Through considering the features of halftone processing, the neural networks technique is applied to adjust the error diffusion kernel adaptively, which can integrate the data embedding with the halftone processing in our algorithm. Experimental results show that the proposed halftone image watermarking is invisible and robust against various signal processions such as JBIG compression, noise adding, cropping, daubing and print-scan.更多还原