【作者】 杨娟；

【导师】 杨丹；

【作者基本信息】 重庆大学 ， 应用数学， 2007， 硕士

【摘要】 数字水印技术是用信号处理的方法在数字化的多媒体数据中嵌入隐蔽标记。它主要应用于数字媒体的版权保护,网络信息的秘密通信以及数据隐藏等方面。本文以静止图像为研究对象,结合目前的研究热点:基于图像特征的第二代数字水印技术和提升小波技术,以如何提高水印算法的鲁棒性和不可见性为主要研究目的。由此,提出了一种基于图像置乱,提升小波技术和图像角点特征检测的盲检测数字水印方案。主要研究工作包括:首先,针对基于第一代小波的多分辨率水印算法运算速度慢、图像的重构质量与变换时延拓边界的方式有关等不足,根据第二代小波变换的特点,给出一种基于小波多级提升来实现的改进型多分辨率图像水印算法。实现了在最低频成分和相应高频成分中水印的快速嵌入和提取。该方案实现简单,对内存需求量小。分别采用Haar、Db2、Db4、9/7小波进行仿真实验,结果表明,该算法不仅保持了传统小波多分辨率图像水印算法的优点,而且弥补了传统小波多分辨率图像水印算法中当滤波器增长时,含水印图像质量下降的不足。本算法较传统算法显著地提高了处理速度,其嵌入的水印具有信息量大、鲁棒性强等优点。其次,研究了基于图像特征的第二代数字图像水印算法,并把多尺度曲率积的鲁棒图像角点检测(MSP)和小波提升方法引入到了第二代数字图像水印算法中。在载体图像三级提升后的最低频成分中提取出图像的角点,然后在角点位置对应的所有高频系数中嵌入预处理过的水印,以兼顾水印的不可见性和鲁棒性要求。在检测时,用同样的方法对含水印图像作三级小波提升变换,在最低频成分中提取出图像的角点。以此为根节点提取其所对应的所有高频系数,在这些系数上作水印嵌入的逆运算,并用事先得到的密钥反变换出水印。所提出的水印方案在旋转、放缩、平移、裁剪等几何攻击比第一代数字水印算法的鲁棒性有显著提高。更多还原

【Abstract】 It is well-known that digital watermarking denotes some digital labels or signatures which are embedded into digital multimedia host data by signal processing. The major application of Digital watermarking lies in copyright protection of digital media, cecure communication on network and data hiding. In this thesis, still images are considered by using the most popular technique, and the second generation watermarking based on the feature of image and lifting-based wavelet are focused on. In order to improve the robustness and imperceptions of watermarking algorithm, the following work have been done:Firstly, a new multi-resolution image watermark algorithm is proposed which is based on wavelet multistage-lifting by analysis of the first-generation wavelet’s deficiencies, such as low speed and the quality of reconstructed image depending on the way extend the boundary and so on. According to the properties of the second-generation wavelet transformation and the basic idea of traditional wavelet multi-resolution, the implementation of the proposed solution is simple and it needs only a little memory. Haar, Db2, Db4 and 9/7 were used in ours experiments. The simulation results showed that the proposed algorithm not only overcomes the deficiency of quality resulted from watermark in the traditional wavelet multi-resolution image watermark algorithm when the filter becomes larger, but also greatly improves the processing speed. The watermark contains a lot of information, moreover, the proposed algorithm has a good robustness and other advantages.Secondly, the second generation watermarking algorithm was researched based on image feature by introducing MSP corner detection algorithm and lifting wavelet. The watermark information was scrambled by using Arnold transformation, and then three-level lifting-based wavelet transformation for the carrier image was done. Corners are detected from the low frequency component of this image. Finally, watermark was embedded into the high frequency coefficients corresponding to the corners. The robustness and imperceptions of the watermark are obtained at the same time. Three-level lifting wavelet transformation for the image contained watermark was performed by using the same method in process of detection. Image corners are detected from the low frequency components. The corners are taken as root nodes for extracting all the corresponding high frequency coefficients. Inverse operation of embedding watermark was performed at those coefficients. And the watermark was obtained using the given key.Experimental results demonstrated that the proposed watermarking algorithm is better robustness than the first generation watermarking algorithm with respect to geometry attack such as RST (Rotation, Scaling and translation) and cut. .更多还原