Digital watermarking is a technique used to protect an author's copyright and has become widespread due to the rapid development of multimedia technologies. In this paper, a novel watermarking algorithm using the nonsubsample shearlet transform is proposed, which combines the directional edge features of an image. A shearlet provides an optimal multiresolution and multidirectional representation of an image based on distributed discontinuities such as edges, which ensures that the embedded watermark does not blur the image. In the proposed algorithm, the nonsubsample shearlet transform is used to decompose the cover image into directional subbands, where different directional subbands represent different directional and textured features. The subband whose texture directionality is strongest is selected to carry the watermark and is thus suitable for the human visual system. Next, singular value decomposition is performed on the selected subband image. Finally, the watermark is embedded in the singular value matrix, which is beneficial for the watermarking robustness and invisibility. In comparison with related watermarking algorithms based on discrete wavelet transforms and nonsubsample contourlet transform domains, experimental results demonstrate that the proposed scheme is highly robust against scaling, cropping, and compression.

Zero-watermarking is a blind digital watermarking method. It has reached the point where the robustness and the imperceptibility can arrive at a good balance. In this paper, a strong robust zero-watermarking scheme is proposed which employs multiresolution and multiscale representation characteristics of nonsubsampled shearlet transform to analyze the direction features of the given image. The effectiveness of the proposed scheme for dealing with many kinds of attack such as compression, noise addition, and scaling is demonstrated by the experimental results. When compared with other zero-watermarking schemes using counterpart transforms like discrete wavelet transform, the experimental results show that the proposed watermarking scheme can get better performance.

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