Optimal detector for multiplicative watermarks embedded in the DFT domain of non-white signals
EURASIP Journal on Applied Signal Processing
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A wavelet-based watermarking method for still images is presented. Watermarks are composed of scaled versions of circularly-symmetric pseudo-random 2D signals in order to attain a spatial self-similar structure with respect to a cartesian grid. Embedding and detection are performed in the wavelet domain thus allowing multi-level detection. The novelty of the method lies in the use of self-similar watermarks (quasi scale-invariant), expected to be robust against geometric transformations, especially scaling. The approach proves rather efficient against many kinds of distortions, such as linear and nonlinear filtering, JPEG and wavelet compression, scaling, cropping and rotation.