Research On Anti-printing And Anti-scanning Digital Watermarking Algorithm On Digital Raster Map

As a cutting-edge technology in the field of information security, digital watermarking technology has been favored in terms of copyright protection of digital data. When this technology has been applied in the application of copyright protection of digital raster maps, the copyright problems such as illegal copying, tampering, and malicious infringement can be solved effectively. With the popularity of high-precision hardware varies from printers, scanners and digital cameras as well as powerful image processing software, printing and scanning have become common methods of copying and distributing digital raster maps. So it becomes rather easy to steal, fake and spread digital raster map maliciously. Therefore it is urgent and important to study and research on anti-printing and anti-scanning digital watermarking technology on digital raster maps.The anti-printing and anti-scanning watermarking technology means that the embedded watermark information can still be detected from digital raster maps after they are printed and scanned. Based on the theory of discrete cosine transform(DCT), considering the characteristics of data forms, this paper conducts research and practice on anti-printing and anti-scanning digital watermarking technology of digital raster maps. The main works are as the following:(1) Taking the features of digital raster maps into consideration, this paper clarifies the characteristics and requirements of digital watermarking technology, discussed the feasibility of this technology being applied in digital raster maps, and concluded the evaluation index of anti-printing and anti-scanning digital watermarking technology on this kind of data.(2)By using the method of brightness transformation and contrast stretch transformation to realize the correction of pixel distortion, and the method of Radon transformation as well as cubic interpolation to achieve the correction of geometric distortion, this paper analyze the effects and changes in the processing of printing and scanning digital raster maps. The conducted experiments results show that these methods can improve the accuracy of extracting watermark from digital raster maps after been printing and scanning.(3) Analyze the change of DCT coefficients of digital raster maps in the frequency domain in the process of printing and scanning, and then find the invariant relation of DCT coefficients’ signs in blocked digital raster maps during this procedure. According to this invariant numeric feature, an anti-printing and anti-scanning digital watermarking algorithm on digital raster maps are proposed, which is able to ensure the robustness of digital watermarking while meeting the requirements of being imperceptible.(4) Study the impact of the process of printing and scanning digital raster maps in the color space, then conclude that the key technologies of enhancing robustness of digital watermarking algorithm lies on color space conversion. After a detailed analysis and comparing, combined with the characteristics of digital raster maps, an anti-printing and anti-scanning digital watermarking algorithm based on color space of CIEL*a*b*is proposed. The experimental results show that the proposed algorithm has higher robustness under the attacks of printing and scanning.