Dual-watermarking algorithm based on Contourlet

In order to improve the robustness of the watermarking algorithm, a dual-watermarking method is proposed based on Contourlet and SVD (Singular Value Decomposition). The method adopts different methods to insert watermark into the low frequency and high frequency of the host image respectively. We make full use of the advantages of the Contourlet transform, that is a flexible multiresolution, local, and directional image expansion was obtained using contour segments. The watermark embedded into the coefficients of the SVD, it will change little when the watermarked image is attacked. When the two watermarks are extracted, we compare them to the original watermarks, and adopt the one whose similarity is higher as the wanted watermark. Two watermarks embedded into the host image using the proposed algorithm will not only increase the watermark capacity, but also improve the robustness. Experimental results show that the proposed algorithm is invisibility and is very robust to many image attacks.