A Cropping Robust Geometric Distortion Correcting Algorithm for Watermarked Image Based on SIFT

This paper proposes a cropping robust geometric distortion correcting algorithm for watermarked image using scale invariant feature transform. Centroid of the original watermarked image is calculated, and the features extracted from the triangles composed of the centroid and the scale invariant feature transform feature points are used to estimate the position of the point in attacked image that correspond to the centroid extracted earlier in original watermarked image, then the geometric distortion can be detected and recovered using centroid angle and centroid distance features extracted from the well matched scale invariant feature transform feature points. Simulation results show that the proposed algorithm can correct the geometrical distortion of watermarked image efficiently.