基于纹理分析的小波域自适应水印研究

【作者】 林晓圆；

【导师】 赵健；

【作者基本信息】 西北大学 ， 通信与信息系统， 2010， 硕士

【摘要】 数字水印技术是当前版权保护的重要手段之一。在实际运用中要求水印在不可见的前提下,有较高的鲁棒性。但是水印不可见性与鲁棒性此消彼长,因此寻求水印不可见性和鲁棒性之间的平衡,是研究水印算法的重中之重。本文在深入分析现有的数字水印算法的基础上,重点研究了基于小波理论的自适应水印算法,针对已有的小波域自适应水印算法的不足进行了改进。本文结合图像拟仿射变换、混沌理论、纹理分析等理论提出了三种自适应水印算法。(1)图像拟仿射变换的小波域自适应水印算法的提出与实现：首先利用图像拟仿射变换来置乱水印图像,然后利用混沌序列抽取子块来组成新载体,最后根据人类视觉系统将水印图像自适应的嵌入到新载体小波分解后的中频中,并通过修改奇异值的方式嵌入,提高了水印算法的安全性。(2)纹理分析与WPT-SVD相结合的自适应水印算法的提出与实现：本算法是在算法一的基础上改进的：从小波分解扩展到小波包分解,拓宽了水印嵌入位置的选择,同时定义了纹理敏感值的计算方法,利用纹理敏感值与块能量的比值来计算各块最佳嵌入强度,嵌入时同样采用修改奇异值的方法,实验结果表明水印有很好的不可见性和鲁棒性。(3)基于纹理分析的小波包自适应盲水印算法的提出与实现：在实际应用中,提取水印时,原始图像不易取得,因此为了进一步提高水印算法的实用性,本算法采用盲水印算法。在前两个算法的基础上,本算法在嵌入水印时,通过判断嵌入点周围点之间的关系确定该点嵌入强度,实现了盲提取。实验证明该算法在经过常见的攻击之后仍能较好的提取水印。本文提出的三种自适应水印算法,实验证明具有很好的鲁棒性和稳健性,有一定的实用价值。更多还原

【Abstract】 Digital watermarking technology is one of the important methods of copyright protection. We must ensure that the watermark is invisible and the embedded watermark images have a strong robustness. Watermark invisibility and robustness is contradictory, so maintaining the balance between invisibility and robustness is the most important thing during the study.The presented three algorithms based on analysis of the existing principles of digital watermarking algorithm and the theory of wavelet-based adaptive digital watermarking algorithm. The main contents are as follows:Algorithm one is "The adaptive digital watermarking algorithm based on quasi affine transformation". First, the algorithm used quasi affine transformation to scramble the watermark image. Second, we extract a number of blocks from the original image using chaotic sequence, and form a new sub-image using those blocks, then make the sub-image go to three wavelet transformations. The encrypted watermarking image was embedded into the sub-image, we embedded watermark by modifying the singular value, then put the blocks of the sub-image into the original position in the original image. Experimental results show that this algorithm is robust and stable to common digital image processing operations.Algorithm two is "The adaptive digital watermarking algorithm based on WPT-SVD(Singular Value Decomposition) and texture analysis". the algorithm is changed based on the algorithm one. We extend from the wavelet decomposition to the wavelet packet decomposition, which greatly expanded the watermark embedding position. This algorithm also defined the texture-sensitive, embedding strength was calculated by the texture-sensitive and wavelet block energy ratio. The watermark was embedded by modifying the singular values. Experimental results show that this algorithm has high robustness.Algorithm three is "The adaptive blind digital watermarking algorithm based on texture analysis". In practice, the original image is difficult to get, so in order to enhance the practicality of watermarking algorithm, this algorithm uses the blind extraction. Embedding strength was calculated by judging the relationship among the points around the embedded point. Experimental results show that this algorithm is robust and stable to common blind digital image processing operations.The experiment shows the three algorithms in the dissertation have strong robust and some practical value.更多还原