In this paper, we propose a digital watermarking algorithm based on the Slant transform for the copyright protection of images. Our earlier research work associated with the fast Hadamard transform for robust watermark embedding and retrieval of images and characters suggests that this transform could also provide a good "hidden" space for digital watermarking. The Slant transform has many similar properties to the Walsh-Hadamard transform. In terms of transform coding, the Slant transform is considered to be a sub-optimum orthogonal transform for energy compaction. For digital watermarking, the energy spread becomes a significant advantage, as there is now a good spread of middle to higher frequencies with significant energies for robust information hiding. In this paper, an analytical comparative study on the performance of the Slant transform adapting our earlier watermarking schemes for fast Hadamrd transform will be performed based on its robustness against various Stirmark attacks. The performance results of the Slant transform for image watermarking against other transforms such as Cosine transform will also be presented.
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