基于二维Logistic混沌映射的DWT数字水印算法

研究了一种基于二维Logistic混沌映射的离散小波变换（discrete wavelet transform,DWT）数字水印算法。该算法提出了一种利用二维Logistic混沌映射打乱原始图像像素点位置的置乱加密方法，用这种加密方法对水印图像做预处理操作，对原始载体图像做三级小波分解，在第三级小波分解后的水平高频和垂直高频子带中绝对值较大的系数中嵌入水印信息，把改变的系数和原小波系数重构后再做逆小波变换，即可获得含水印图像。水印的提取过程就是水印嵌入的逆过程。实验结果表明，该算法不仅有很好的透明性，而且对噪声攻击、JPEG压缩攻击和剪切攻击有很好的鲁棒性，并且提取出的水印有较高的安全性。

DWT digital watermarking algorithm based on 2D logistic chaos mapping

In this paper, the discrete wavelet transform (DWT) digital watermarking algorithm based on 2D logistic chaos mapping is proposed. Firstly we take advantage of the chaotic sequence made by chaos mapping to encryption the watermark image. Then we put the encrypted watermark image embedded into the large coefficients in the horizontal and vertical high frequency sub-band of three-level DWT. Lastly, we put the combination coefficients of the changed wavelet coefficients and original wavelet coefficients to IDWT, and we got the watermarked image. Experiment results show that the algorithm is not only of good hiding and good robustness to noise, JPEG compression and cut attack, but also with security.