Robust block-based watermarking scheme in curvelet domain

In this paper, a robust block-based watermarking scheme operating in curvelet domain is proposed. Curvelet transform directly take the edge as the basic representation element; it provides optimally sparse representations of objects along a general curve with bounded curvature. The image is partitioned into small blocks; an edge map is computed to determine the edge strength for each block. Fast discrete curvelet transforms is employed to decompose the selected block into curvelet domain. We embedded the watermark into the selected blocks, scale and curvelet coefficients taking into account both the transparency and the robustness. As usual, the watermarks are blindly detected using a correlation detector. We take the Radon transform of the edge map of the cover image to synchronize the location of embedded watermark before applying the detector. Experimental results show that the scheme is robust to severe image degradation as well as geometrical attacks.