【摘要】 在基于小波域的盲水印系统中,由于小波变换的局部性,致使水印的嵌入可能会给原始图像带来类似于图像压缩中产生的“块效应”。为了在保持强度不变的前提下进一步提高水印的不可视性,提出了一种基于图像置乱预处理的小波域盲水印算法,即先将原始图像置乱,而后再将水印嵌入到图像小波域中,以达到将水印所引入的“块效应”化整为零地分布到图像的不同部分的目的,从而在很大程度上提高了水印视觉上的“不可感知性”。试验证明,这种算法是有效的。另外,经过置乱操作的图像,小波变换后得到的小波高频系数服从高斯分布,这就使得线性相关检测在这个水印系统中能够达到最优。更多还原

【Abstract】 In the digital watermarking system based on the discrete wavelet transform, because of its localization, watermarking embedding often introduces some error just like “block effects” in the image compression. In order to increase the invisibility of the watermarking with the embedding strength being kept, in this paper an algorithm is presented that the image is scrambled firstly before embedding the watermark into the wavelet domain, so that “block effect” generated by the watermark can be distributed to different parts of the image and then the invisibility of the watermark is improved to a great extent. Experiments show that this idea is feasible. Moreover, it is shown from some standard images that the distribution of the wavelet coefficients of the corresponding scrambled images is approximately Gaussian, which makes the linear correlation detector in this watermarking system be optimal.更多还原