Study On Lossless Digital Watermarking Technology And Algorithm For Vector Map

With the constant deepening of vector map in the actual application, safety vector map copyright protection and data authentication and other issues have become increasingly prominent. As an important means of copyright protection of the vector map, digital watermarking technology has been overwhelming concerned by majority of experts and scholars, research institutions, This paper takes on the vector map lossless digital watermarking technology as the theme, studied the available vectors of vector map digital watermarking, vector map lossless watermarking framework model, in order to improve the robustness of the lossless watermarking algorithm, the watermark capacity and etc, a series of vector map lossless watermarking algorithm was studied, the main research results of this paper are summarized as follows:(1) Analysis of lossless digital watermarking techonology for vector map. Based on a thorough analysis of the vector map’s data content and data structure, a general model of lossless digital watermarking for vector map is given, Analyized the embedding position of lossless digital watermarking for vector and according to the characteristics of vector map data, studied he evaluation index of digital watermarking algorithm for vector map.(2) Study on the zero watermarking for vector map. According to the data features of the vector map, a framework model of zero watermarking for vector map is presented, analyzed the theoretical foundation of creating meaningful zero watermark. In view of the poor robustness of traditional watermarking algorithm to resist attack, according to the spatial character and the attribute character of vector map respectively, two kinds of zero watermarking scheme were designed:a zero watermarking algorithm based on feature point and block for vector map, through feature point extraction, block processing with the improved Quad tree (MQUAD), a kind of zero watermarking algorithm was designed effective against map geometric transformation (translation, rotation, scaling), data compression, vertex deletion, and map clipping; a zero watermarking scheme based on feature coding of vector map, analyzed the properties of feasibility as structural feature information using the feature code, using the stability of feature code to construct zero watermarking, which effectively improves the robustness of the algorithm against geometric transformations (translation, rotation, scaling), map generalization especially the feature editing etc.(3) The improved reversible watermarking algorithm based on difference expansion for vector map is put forward. The difference expansion algorithm is simple, has large watermarking capacity etc. Based on the traditional difference expansion algorithm, improved the calculation formula for vertex coordinates, it does not need to calculate the mean between the vertices, only the first vertex coordinates need embedding with the watermark, except the first vertex coordinates not changing, the other vertex coordinates change only once. The proposed algorithm provides a solution to improve the embedding capacity, efficiency of the algorithm, reduce the data error,and enhance the security.(4)A reversible watermarking algorithm based on histogram shifting for vector map is put forward. According to the weak correlation between the coordinates of the vertices, the chaotic characteristics of data storage, a reversible watermarking algorithm based on sorting and histogram shifting for vector maps is designed, sorting the vector map vertices in order to enhance the correlation between adjacent vertices to increase the watermark capacity; using histogram shifting instead of difference expansion to reduce the data error, at the same time, HASH value of the original vector map embedded with secret information to further improve the ability of copyright authentication, the embedding capacity algorithm has high and relatively small data error, and is robust to the coordinate translation, data reordering attack.(5) A high-capacity reversible watermarking algorithm for vector map is put forward. The evaluation index of watermark capacity was introduced, and the difference expansion algorithm and histogram shifting algorithm of watermarking capacity were analized. Difference expansion algorithm of vector map watermarking capacity depends on the vertex expandable difference, for small data map watermark capacity is not high, and the histogram shifting algorithm generated more additional information because of multi-layer embedding, which leads tolow embedding rate. Aiming at the limitation of the two kinds of algorithms, a large capacity reversible watermarking based on difference translation and parity for vector algorithm was designed, watermark capacity is not affected by the correlation of vertex coordinates, it effectively improves the watermark capacity, at the same time it bring to smaller error compared with the difference expansion algorithm and histogram shift algorithm.