A Study On Forgery Prevention Algorithm Of Print Materials Based On Digital Watermarking

This paper is intended to advance an effective printing forgery prevention algorithm basing on digital watermarking technology.We analyze several theories which the algorithm will be involved, and fully consider visibility, robust and security of the embedded image. According to the difference of embedded watermark, the algorithm has two parts as follows:First, we assume that the embedded watermark is binary image. The original image is transformed by 8×8 block Hadamard. The embedded watermark is shuffled and we get the key. Then the watermark is embedded through changing the polarity of transform coefficients.Second, we assume that the embedded watermark is a string. Spread spectrum the watermark, then the watermark is embedded the same way as the binary image.The print-scan image should be preprocessed before extract watermark. First we detect the print-scan image edge which using Sobel operator of edge detection. Then the print-scan image is emended by Radon Transform. Finally, it is resumed the original size, and we extract the watermark.The results show that the algorithm can extract watermark in various attacks and makes a good effect on the forgery prevention.