Research On High Capacity Reversible Watermarking Scheme For2-D Engineering Graphics

In recent years, with the rapid development of network technology, thetransmission and sharing of digital products have become more and more convenient.But the consequent security issues such as copyright protection have caused people’sgreat attention. Digital watermarking, as a kind of new technology for copyrightprotection, can provide an effective solution for copyright protection. For some areaslike medicine, military and machining, with very high demands on the integrity of thedata, no distortion is allowed when protecting its copyright by using digitalwatermarking method. To meet this actual application demand, reversible digitalwatermarking has become a hotspot in recent years.In the industrial design, since2-D CAD engineering graphics are the main carriersof computer-aided design, the research on their copyright protection has very importantand realistic meanings. With the high demands on date accuracy of CAD graphics inpractice, research on2-D CAD engineering graphics should be reversible in properaccuracy range. However, at present, the reversible watermarking research mainlyfocuses on digital image field, while there is very few research on digital graphicsespecially2-D CAD engineering graphics.In this thesis, the overseas and domestic research status of reversible watermarkingtechnique for2-D CAD engineering graphics is analyzed in detail, followed by the basicknowledge about digital watermarking for2-D CAD engineering graphics. Then theimproved quantization index modulation algorithm and improved difference expansionalgorithm are introduced. At last based on those two existing related methods, a highcapacity reversible watermarking scheme for2-D CAD engineering graphics isproposed. The main work is as follows:①The related knowledge about digital watermarking is introduced, followed bythe feature and application background of vector graphics watermarking. Then a briefintroduction to the feature and watermarking requirement of2-D CAD engineeringgraphics is made.②A reversible watermarking algorithm based on improved quantization indexmodulation (IQIM) technique is introduced. It has a good imperceptibility after embeddingwatermark, but not every vertex in graphics can be embeddable.③A reversible watermarking algorithm based on improved difference expansion (IDE) technique is introduced. It makes every vertex embeddable, but it has a muchworse imperceptibility than IQIM after embedding watermark.④In this thesis, based on the improved quantization index modulation (IQIM), bycombining IQIM and IDE algorithms, a high capacity reversible watermarking schemeis proposed for2-D CAD engineering graphics. The proposed scheme can increase thealmost two times embedding capacity than before with the same imperceptibility.Besides, it has good robustness.Finally, the conclusions and drawbacks of this thesis are given. And the futuredirection is also discussed.