A Study On Forgery Prevention Algorithm Of Digital Watermarking For Printing Image

A newest algorithm of digital watermarking for color image is proposed in this paper, which proposed a new way for the research of forgery prevention techniques. The fruits can be applied to presswork of having copyright, such as securities, pass, etc, which can make forgery prevention techniques and safety printing progress and has important meaning in national economy's development.The main works include: (1) The color distortions of color printing pictures by printing and scan are analyzed and a newest algorithm of digital watermarking for color image is proposed. The main innovation of this algorithm consists in its design making use of the excellence of color space, discrete wavelet transform (DWT) and singular value discrete (SVD). The CIE1976L a b color space is proposed in inserting watermark and many same watermarks are inserted, at the same time, into the singular value of coefficients of DWT. So that the loss brought by print-scan process can be reduced and the robustness and safety of watermark can be improved. (2) According to the disturbance theory of singular value, the intensity of inserting can be adjusted to estimate the error between host image and marked image, by means of the method of color difference. And novel-evaluating methods of watermark invisibleness and aloneness are promoted. (3) The experiment is designed based on black-box theory. And the insertion and extraction of watermarking is programmed by means of computer. In addition, the printer and scanner of having high resolution are adopted in experiment to obtain the exact datum. Finally, the validity of algorithm is evaluated synthetically.The proposed algorithm is robust against common print-scan process and image processing operations. The results of the research realize color printing products copyright protection and forgery prevention. Compared to other watermarking algorithm, the invisibleness and robustness of watermark are better. And by comparing to other forgery prevention techniques, the proposed techniques can decrease the cost of production and be completed easily.