A colour image watermarking technique resistant to affine geometric attacks

This paper presents a colour image watermarking scheme resistant to affine geometric distortions. The technique involves embedding of the watermark in the host image in the Discrete Cosine Transform (DCT) domain in a spread-spectrum format. Harris corner detector based feature-points are then employed to get Delaunay triangulation which is used to reverse geometric attacks before attempting to extract the watermark. In some instances the geometric attack may lead to loss of feature-points resulting in the recovery of low quality watermark. In this paper we propose a scheme of estimating geometric attacks by taking the mean of selected triangles in the Delaunay tessellation. Computer simulation using MATLAB has been used to show the robustness of the proposed scheme.