| With the rapid development of Internet in the Information Age, people’s life has greatly improve, but it also makes the access to digital images and other digital media much more easier, what’s worse,the development of scanning and printing technology aggravate this trend in recent years. It is a great challenge to copyright protection of digital media.In order to deal with this problem, many information security methods have been used to protect digital media. Invisibility and robustness as it is, digital watermark has attracted more and more attention of researchers. Many papers have already proposed some high robustness algorithms, some of the algorithms can even resist print-scan attack, but adaptability of this algorithm is very poor.Based on the research of the existing theory, this paper proposed a digital watermarking algorithm for print and scan process using genetic algorithm.The main research and innovative works are expressed as follows:1. This paper analyzed the existing research result and pointed the shortages of the existing research. Introduce the basic principle of genetic algorithm and studied the existing research results of the combination of genetic algorithm and digital watermark scheme. Analyzed the scan and print process and discussed its impact on digital images, based on the analysis this paper summarized all kinds of attacks to watermarking system during print and scan process.2. By discussing the changes of DCT coefficients, this paper finds an invariants during print and scan process, combined with watermark Spread Spectrum technology, this paper proposes a print-scan resistant digital watermarking algorithm based on DCT and watermark. Spread Spectrum. Experiment results have shown that this algorithm can resist to the print-and-scan attacks if the embedding intensity and position is chosen properly. Since the embedding intensity and position must be set manually, the adaptability of this algorithm is very poor.3. In order to solve this problem, genetic algorithm is applied in this paper to optimize the embedding intensity and position of. the watermark. Experiment results have shown that with GA the algorithm can resist to the print-and-scan attacks much better. |
