Research And Improvement Of Source Investigation System Based On Text Digital Watermarking

With the rapid development of computer and Internet, it becomes a easy process that storing and exchanging information. By using computer, Internet, scanner, printer, fax etc, people could easily get, store, copy, and broadcast multimedia information, sending information everywhere on the world. There is also a security problem brought in, that is the governmental or commercial crucial files might be stolen and spread abroad illegally. It is difficult to determine the source of said files.Source investigation system utilizes the technique of text digital watermarking to determine the source of illegal files in both digital and analog domain, and provides security assurance to the files of e-commerce and e-government. Interrogation system based on text digital watermarking is a newly appeared subject, which would be widely used in the age of information. It is valuable and meaningful of doing research on this subject.In this paper, digital watermarking technique and interrogation system is introduced. It is also analyzed that the problems of the existed digital watermarking technique and interrogation system. The problems to be solved are mainly about:(1) watermarking takes much time when files contain many pages, which results in low efficiency, (2) watermarking extraction might cause error, which results in low accuracy. In this paper, research is done in order to improve the performance of whole system. The main research contents are as follows:(1) It is analyzed that the whole system. Low virtual print speed and low image preprocess quality are critical reasons which result in low system performance. The virtual printer module is redesigned to improve processing efficiency. Research on algorithm of image skew detection and correction before watermark extraction has been done to improve image preprocess quality.(2) Techniques related to virtual print is researched. A software platform based on virtual printer is redesigned for adding watermarking. It improves the quality and speed of the image conversion, provides flexible method of adding watermarking. The software platform could be applied to the interrogation system so that the performance of system is improved.(3) The binarization algorithm of text image before watermarking extraction is researched. The performance of typical binarization algorithm is analyzed. Speed and quality of different binarization algorithm is compared. A image block algorithm is proposed, which could achieve better quality for the binarization of the Uneven illumination image. The research above is helpful in improving the image preprocess module of interrogation system.(4) The algorithm of image skew detection and correction before text watermarking extraction is researched. A method based on blank line cumulative for image skew detection is proposed. The method provides fast and accurate image skew detection to improve the image preprocess module of interrogation system.