A watermarking algorithm based on direction of image specific edge

A novel watermarking method to construct watermarking synchronization information by using Directionlet was proposed. The direction of the image specific edge is obtained as the transform direction of Directionlet, the alignment direction of Directionlet is achieved by forming a invariable angle with the transform direction. The generator matrix of the lattice is given by the two direction vectors. Several copies of watermark are inserted into the frequency domain of all the cosets of the lattice. In order to eliminate the effect of geometric attacks to watermark detection, the watermark is detected in the reference frame established by using the direction of the image specific edge as its an coordinate axis. The main contribution of this paper is the introduction of Directionlet along specific direction for watermark embedding and extraction, which enables the watermark more robust against geometric transformations. Experimental results show the proposed watermarking algorithm outperforms the wavelet-based and contourlet-based in terms of transparency as well as robustness.