基于小波包变换和离散余弦变换的双水印算法.pdf

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that the algorithm possesses the following advantages.
Embedding the watermarks in the low and high frequency of the host image W PD imp roves the watermark resistance to
different attacks. Considering the DCT energy comp ression ability and the ability of ridding correlation, the use of DCT in
the lowest frequency band of theW PD enhances the watermark robustness and invisibility. Two watermarks embedded in the
host image not only increase the watermark capacity, but also imp rove the serviceability of the algorithm.
Keywords　digital watermark, wavelet packet transform, discrete cosine transform, human visual system
要信息集中到最少的低频系数上 ,然后在不同频段
1　引 　言 系数上嵌入水印。由于水印嵌入到低频系数上虽然
鲁棒性好 ,但容易使图像产生较大的失真 ,而嵌入到
目前 ,图像数字水印算法主要基于空域 、变换 高频系数上虽然不可视性好 ,但水印容易被压缩或
域、压缩域、生理模型、抗几何攻击等多方面。比较 低通滤波操作去掉 ,因此 ,一般算法都考虑把水印嵌
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常用的 是基 于离散 余弦变 换 [ 1 3 ] 和离 散 小 波 变 入到中频系数上