Geometric attack is an open problem to digital watermark.Current techniques could not solve it effectively

especially for block-based watermarking.In this paper

a new method is proposed to provide an easy-use and robust detection to geometric transform parameters.A rectangle frame in an image is utilized to estimate the coefficients of geometric attack and locate watermarking.Median filtering and sharpening on the rectangle frame are used to enable a more accurate estimation.Cropping attack is also detected by the method.The geometric distortion's correction based on the estimation results is performed to make watermark synchronized by the template matching.Experimental results verify that this method provides an accurate estimation and a nearly lossless restoration of watermark.