Research On The Algorithms Of Reversible Watermarking Of 2-Dimentional CAD Engineering Graphic

Along with the rapid development of network technology, digital media has become very easy to share and transmit, followed by security issues such as copyright protection has become increasingly prominent. As the main carrier in computer-aided design application, two-dimensional CAD engineering graphics have been widely used in industrial design applications, what make it is very significant to protect its copyright from infringement.Digital watermarking technology provides an effective solution for copyright protection, which has become a research hotspot in recent years. Compared with traditional robust watermarking technology, reversible or lossless watermarking technology, which is raised in recent years, can restore original media lossless or approximately lossless. Therefore, it is particularly suitable for these digital medias with high precision requirement, such as the two-dimensional CAD engineering graphics. At present, the reversible watermarking technology research mainly focuses on digital image, and there are no papers published yet in the field of the reversible watermarking research on two-dimensional CAD drawing.In this thesis, a detailed analysis of the research status and existing problems of the current reversible watermarking and digital watermarking technology for two-dimensional CAD enginerring graphics are presented first, and then we are in-depth study of the reversible watermarking technology for two-dimensional CAD engineering graphics, and proposed three reversible watermarking algorithms. This work includes:1. Proposesed an improved quantization index modulation (IQIM) method, and applied it to two-dimensional CAD drawings watermarking. Because the method does not need to embed the recover information of the cover media, the watermark capacity can be greatly improved.2. Utilize the advantages of good energy concentration and translation invariance of wavelet transform, and presented a reversible watermarking algorithm for two-dimensional CAD engineering graphics based on wavelet transform. Watermark is embedded in wavelet domain of the vertex data in engineering graphic by using IQIM method, to obtain better invisibility and robustness.3. Motivated by traditional difference expansion method, a reversible watermarking algorithm for two-dimensional CAD engineering graphics based on improved difference expansion method is proposed. According to the characteristics of the data on two-dimensional CAD engineering graphics, watermark is embedded in the scale factor of vertex data, and the watermark capacity is greater than traditional difference expansion method.4. A watermarking software system for two-dimensional CAD engineering graphics is designed and implemented, to verify the validity of the three algorithms proposed in this thesis.All of the three reversible watermarking algorithm proposed in this thesis can not only avoid the shortcomings of the high data relationship demand on cover media for existing reversible watermarking technology, but also can be applicable to these digital media with the double type of data, such as 3D models and vector maps, which has a good scalability.