基于计算全息的Contourlet域数字水印算法

目的提出一种基于计算全息的contourlet域数字水印算法。方法首先,利用共轭对称延拓傅里叶计算全息方法,将原始二值水印图像生成全息水印图像;然后,将原始图像进行二级contourlet变换,得到8个中频方向子带系数;最后,将全息水印嵌入在其中频系数中。结果该方法可以有效抵抗高斯滤波、中值滤波和均值滤波以及打印-扫描攻击,同时,对噪声攻击、裁切攻击和JPEG压缩攻击也有很强的抵抗能力。在水印提取时无需原始图像,属于盲水印算法。结论该算法可以广泛应用于数字图像的版权保护中。

Digital Watermarking Algorithm in Contourlet Domain Based on Computer Generated Holography

Objective To propose a digital watermarking algorithm in contourlet domain based on computer generated holography. Methods Firstly, a binary watermarks was converted to a holographic watermark using the computer generated holography by the conjugate-symmetric extension. Secondly, the original image was subjected to two-dimensional contourlet transform, and the intermediate frequency was transformed into eight directional subband coefficients. Finally, the holographic watermark was embedded into one directional subband coefficients. Results Experimental results demonstrated that the proposed method could well resist attacks such as low-pass filtering, noise, cropping and JPEG lossy compression. And the algorithm could also survive print-scan attack. The original image was not needed during watermark extraction. The proposed algorithm was blind. Conclusion The watermarking algorithm proposed could be widely used in copyright protection of digital images.