Research On Reversible Watermarking For2D CAD Engineering Graphics

With the high-speed developing of the network information and digital multimedia technology,2D CAD engineering graphics are widely used in many industries. And the piracy issues such as illegal using, modifying and editing the2D CAD engineering graphics, are also getting worse. Digital watermark technology has attracted more and more attention because it is an effective method to deal with the copyright protection. In order to meet the small data redundancy and the high precision of the2D CAD engineering graphics, we use the reversible watermark to embed the watermark. However, recently the reversible watermark technology has been widely used in the copyright protection of the digital graphics while rarely used in the area of2D CAD engineering graphics. This paper deeply analysis the algorithms and the existing problem about2D vector graphics in and abroad. And combined with the high accuracy requirements of the2D CAD engineering graphics, this paper focuses on the reversible watermarking algorithm for the2D CAD engineering graphics. In this paper, two algorithms have been made some improvements of the existing2D CAD engineering algorithm to enhance the robustness or the invisibility of the watermark.First, propose an algorithm based on sub-block of the2D CAD engineering graphics. As the2D CAD engineering graphics’watermark technology have weak ability to resistant attack such the deleting and modifying. Adopt the idea to repeat embedded two or more watermark information into the engineering graphics. First, use the composite chaotic sequence to encrypt the watermark information to improve the security of the watermark. Then, divide the2D CAD engineering graphic into several blocks to embed watermark which improve the ability to resist the attack of deleting. We extract vertex information of the linear entities by each block, do the LPM transform of the relative vertex coordinates, finally, embed the watermark information into the detailed coefficients of morphological wavelet transform by using the improved quantization index modulation.Secondly, propose a reversible watermarking algorithm in the DFT domain using the improved interpolated extension algorithm. Use the vertex coordinates to construct sequence of the complex. And use the complex to do the DFT transformation. Then, use the improved interpolated extension algorithm to embed the watermark into the amplitude of the DFT coefficients. And use the algorithm to recover the data of2D CAD engineering graphics. This algorithm has achieved the reversibility watermark. And it also has a good ability of irreversibility. In terms of watermark preprocessing, use the method of changing the embedding strength of watermark, to develop the embedding capacity of watermark.Finally, Design a simple two-dimensional CAD engineering graphics copyright protection system to protect and authenticate the copyright of two-dimensional CAD engineering. Achieve the ability of the drawing, editing, watermark information encryption, watermark embedding and extraction, recovering the data of two-dimensional CAD engineering graphics and doing attack testing.