document: Geometrically invariant watermarking using feature points This paper presents a new approach for watermarking of digital images providing robustness to geometrical distortions . The weaknesses of classical watermarking methods to geometrical distortions are outlined first . Geometrical distortions can be decomposed into two classes : global transformations such as rotations and translations and local transformations such as the StirMark attack . An overview of existing self-synchronizing schemes is then presented . Theses schemes can use periodical properties of the mark , invariant properties of transforms , template insertion , or information provided by the original image to counter geometrical distortions . Thereafter , a new class of watermarking schemes using the image content is presented . We propose an embedding and detection scheme where the mark is bound with a content descriptor defined by salient points . Three different types of feature points are studied and their robustness to geometrical transformations is evaluated to develop an enhanced detector . The embedding of the signature is done by extracting feature points of the image and performing a Delaunay tessellation on the set of points . The mark is embedded using a classical additive scheme inside each triangle of the tessellation . The detection is done using correlation properties on the different triangles . The performance of the presented scheme is evaluated after JPEG compression , geometrical attack and transformations . Results show that the fact that the scheme is robust to these different manipulations . Finally , in our concluding remarks , we analyze the different perspectives of such content-based watermarking scheme
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