改进的层式DCT在数字水印技术中的应用

数字水印问题研究中,DCT块效应是困扰版权保护的一大难点.结合小波特性,提出一种改进的层式DCT算法,并应用于数字水印.将DCT变换后所得子块的低中频系数分别抽样,然后将水印信息的变换域量值分别叠加到原始载体经改进的层式DCT变换后的低中频系数中,同时对改进的层式DCT变换的分层层数进行了研究.实验结果表明,水印方案具有很好的整体去方块效应,提高了水印的不可见性,对抗压缩、剪切等常规几何攻击具有较强的鲁棒性,并且两者之间达到了一个较好的平衡.进一步扩大了层式DCT的实际应用.

Improved Layer DCT Applied to Digital Watermark

In the research of digital watermark,blocking-artifact problem is a very big difficulty of copyright protection.An improved layer DCT algorithm is proposed based on wavelet features,and it is applied to the digital watermark.The low-frequency and middle-frequency coefficients were extracted after DCT transform and reconstructed by the spatial position.The digital watermark was embedded in low-frequency and middle-frequency domain,and the number of layers which should be chosen was researched.The result shows that the improved layer DCT algorithm does well in removing the blocking artifact,and satisfies the request of invisibility.The improved layer DCT algorithm has better robustness with the attacking experiments,and the practical application of layer DCT is enlarged.