In order to improve the robustness of watermarking scheme against geometrical attacks, this paper proposes a new image watermarking scheme which is robust to RST attacks with cropping by improving Fourier-Mellin transform based wavelet transform. The proposed scheme decomposes the original image through wavelet transform and obtain the low-frequency domain, and then embed and detect the watermark in this domain. Unlike FMW, our method uses log-polar map (LPM) in the spatial domain for scaling invariance, while translation invariance is provided by the use of an invariant centroid as the origin of LPM. This invariant centroid makes sure that the origin of LPM after geometrical attack is as same as before. For this, its calculation method is proposed. Also according to the DFT property of accumulating, 2-D DFT is performed on the LPM image and the magnitude spectrum extracted to provide a domain that is rotation invariant The resulting domain, which is invariant to RST, is then used as the watermark-embedding domain. Experimental results demonstrate that the proposed scheme is robust to RST attacks.
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