A geometric distortion correction method for lithographic watermarked authentication images
Yong Xie, Juan Li, Juanjuan Wang, Chuan-yong Liu · Proceedings of SPIE, the International Society for Optical Engineering/Proceedings of SPIE · 2014
The anti-counterfeiting watermarked images of lithographic prints must be transformed into digital images by scanner or camera before authenticating. The obtained images usually happen to geometric distortion so as to influence the watermark extraction. A geometric distortion correction method for the lithographic watermarked authentication images is proposed in this paper. Hough transform is used to detect the edge lines or corner points, and then unites with the nature of the oblique distortion or the perspective transformation model to correct the distortion. Finally, morphological filtering is used to revise the corrected images. Experiments results demonstrate the method can correct the geometric distortion well and the watermarking image can be extracted and clear enough to authentication.