为了使水印具有更强的鲁棒性和更广泛的适用性,提出了一种基于小波包变换(WPT)和离散余弦变换(DCT)的双水印算法。该算法是在WPT域和DCT域,结合人眼视觉特性(HVS)在宿主图像小波包分解的高低频带,选择不同的方法分别嵌入一个水印,由于双水印充分利用了小波包高低频域的不同抗攻击能力和DCT域的聚能、去相关能力,从而增强了算法的鲁棒性。仿真实验表明,该双水印算法不仅具有较强的鲁棒性和不可视性,并有较大的水印添加容量和更广泛的适用性。

A bi-watermarking algorithm basing on wavelet packet transform(WPT) and discrete cosine transform(DCT) is proposed in this paper.With the human visual system(HVS) in the domain of WPT and DCT,the algorithm adopts different methods to insert one watermark in the low frequency and high frequency of the host image wavelet packet decomposition(WPD) respectively.Experimental results show that the algorithm possesses the following advantages.Embedding the watermarks in the low and high frequency of the host image WPD improves the watermark resistance to different attacks.Considering the DCT energy compression ability and the ability of ridding correlation,the use of DCT in the lowest frequency band of the WPD enhances the watermark robustness and invisibility.Two watermarks embedded in the host image not only increase the watermark capacity,but also improve the serviceability of the algorithm.