基于分块DCT的盲水印算法的研究

为了在保持嵌入强度不变的前提下进一步增强数字水印的不可见性，提出一种自适应盲水印算法，首先将水印图像进行比特位分解，提取其中的一层作为预处理的水印信号，并对其进行置乱处理；然后利用Logistic映射的混沌序列进行调制，构成水印；最后，利用视觉掩蔽特性对载体图像的DCT块进行分类，根据分类结果，对相应的斜方向相邻频域系数之间的差值进行量化和调整以嵌入水印．实验结果表明，该算法对常见的图像处理具有较好的鲁棒性．

Research on blind watermarking algorithm based on block-DCT

To increase the invisibility of a digital watermarking while keeping its embedding strength,an adaptive blind watermarking algorithm is presented.Frist,the image's watermark was decomposed into a series of binary images and one bit plane was taken as the preprocessing watermark.Then,it was scrambled and modulated by Logistic mapping a chaotic sequence to constitute the watermark.Finally,based on the human visual system, discrete cosine transformation(DCT) blocks of the original image were classified.According to the classification,the differences between adjacent DCT coefficients in inclined direction were quantified and adjusted to embed the watermark.The experimental results show that the algorithm is robust to usual image manipulations.