ABSTRACT
Objective To propose a double watermarking algorithm based on contourlet transform and speckle detection to automatically select the region of interest(ROI)for solving the problems of copyright infringement and malicious destruction of CT and MRI images.Methods The method used speckle detection and singular value decomposition to select the most relevant location in the low frequency domain of the medical image contourlet wave as the ROI,generated a zero-watermarked image in ROI for protecting image integrity,and embed the ROI zero-watermark and the copyright watermark together in the region of non-interest.Results Compared with other double watermarking algorithms,the double watermarking algorithm could greatly improve the invisibility of the carrier image after the attack.The double watermarked images had a structure similarity index measure higher than 94%.Conclusion The proposed double watermarking algorithm incorporating speckle detection and contourlet transform has better robustness against conventional attacks and geometric attacks,and significantly improves the visual quality of carrier images.