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.