Research And Realization Of Documents Digital Watermarking Algorithm Based On Chinese PDF

The fast development of Internet industry has provided much convenience for the transmission of multi-media information. With the present technology, we can get the exact duplicate of the original data, but how could the patent right and the financial benefit of the original author be protected and how could we ensure the security of the data ultimate users get? As a hot topic in the field of the security of the multi-media information, digital watermark technology has been employed as an effective measure to protect intellectual rights.Among different kinds of multi-media data, it is much easier for digital documents to be transmitted and copied, but on the other hand, words documents are more valuable than pictures and sounds. Therefore the present thesis conducted quite detailed research into the newly-sprung protection technique for documents digital watermarking, and specific analysis of the current research situation, categories and key technique of it has also been conducted. The purpose of embedding watermarking could be realized through the analysis of the normal formats of common documents, the hypothesis of word shifting and line shifting based upon airspace spatial domain, as well as the visual features of human sight.Due to the larger redundancy of static digital gray level images, through embedding watermarking, much better effect could be achieved than the one in word documents, and the researches in the scope has been well conducted. Therefore the way of image digital watermarking is introduced into word digital watermarking, i.e. the way of binary image of word digital watermarking. But due to the difference in actual application, at the time of introducing the basic measures of image watermarking in the scope of transform domain, special process must be adopted to enhance the gray level and binary image of the object of the binary image. Experiments indicate that better robustness and invisibility could be achieved through this way.As far as application is concerned, the thesis attached special importance to the digital watermarking of PDF document which has developed into the major document format in internet information transmission. The thesis aims to realize the protection of the genuineness of document content through embedding the watermarking information generated from character codes of the original documentsinto the character margin of document. Experiments indicate that the genuineness of documents could be effectively judged through the method in the thesis. This digital watermark technology based on character codes could be quite effective in protecting documents from being intentionally changed, and consequently offers a new research approach for the watermark algorithm of format documents.