Abstract
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.
Highlights
Given the rapid development of digital data and associated technologies, copyright protection of multimedia has become a challenging problem
For Laplacian pyramid (LP) decomposition, an approximate image is generated, and after directional filter bank (DFB), 8 and 16 different directional subbands are obtained in the respective scale
This paper proposes a method based on statistical measurements for calculating image directionality from the directional histogram [24, 25]
Summary
Given the rapid development of digital data and associated technologies, copyright protection of multimedia has become a challenging problem. A multiresolution method, provides a tremendously effective representation of images containing edges [13, 14] and is widely used in watermarking algorithms [15,16,17,18]. Based on previous studies [17], a watermarking algorithm was proposed using the shearlet transform and bidiagonal singular value to achieve balance between robustness and imperceptibility. A nonsubsample shearlet transform (NSST), along with a combination of Laplace and shear filters, is used to decompose an image into different scales and directional subbands. The proposed watermarking scheme has high robustness and imperceptibility depending on texture directionality in the NSST domain.
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