基于离散小波变换和混沌加密的图像水印算法

Watermarking Algorithm Based on DWT and Chaotic Encryption

文中提出了一种基于离散小波变换和混沌加密的数字水印新算法,采用二维混沌变换对水印图像加密;对载体图像进行多分辨离散小波变换,应用小波系数判断载体图像的纹理复杂程度后,依据人眼的视觉系统(HVS)特性,将水印信号嵌入到图像的低频部分,对图像的不同分解层分别选取不同的纹理阈值和水印嵌入强度,将数字水印嵌入到相同分辨层的原始图像中,提高了水印算法的鲁棒性。在检测和提取水印时,通过水印相似度(NC)和峰值信噪比(PNSR)评价水印质量,实验结果表明提出的算法可以抵抗剪裁、JPEG压缩、滤波等几何攻击,算法简单,计算复杂度小,兼顾了水印的不可见性和鲁棒性。

A new digital watermarking algorithm is proposed in this paper, based on discrete wavelet transform and chaotic encrypt. Two-dimension chaotic transform is applied to encrypt watermarking image; multi-resolution discrete wavelet is used to transform carrier image, and the wavelet coefficients is applied to determined complicate degree of veins of image. In conjunction with the character of human vision system （ HVS）, watermarking is embedded in low frequency part of image. Selecting different veins threshold and embedded intensity for different wavelet layer, watermarking is embedded in corresponding image with the same resolution, as a result, robustness of the watermarking algorithm is improved. When detecting and extracting watermarking, similar degree NC and peak noise to signal ration PNSR is used as judge criterion of quality of watermarking. The experiment results indicate that this algorithm can resist geometry attacks, such as crop, jPEG compression, filter and so on. It is simple with less computation amount and the watermarking is invisible and robust.