A Novel Synchronisation Approach for Digital Image Watermarking Based on Scale Invariant Feature Point Detector

The resistance of watermarking schemes against geometrical distortions is one of the still opened and challenging problems in the field of watermarking. In this paper a novel approach for watermark synchronization based on use of scale invariant feature point detector is proposed. The most important feature of this technique is that it does not require the presence of original image. The main idea consists of extracting the robust feature points with scale invariant feature point detector and to embed in the neighborhood of every feature point two information, which can be later used to detect the parameters of undergone geometrical transformations. When the affine transformation, consisted of image rotation, scaling, cropping or combination of them, occurs, it is enough correctly to detect at least from one feature point neighborhood these two information. After that, the parameters of rotation and scaling can be easily calculated.