The Research On Key Technology Of Secure Authentication Watermarking For Engineering Graphics

With the development of computer application technology,computer aided design is widely used in industrial production,and Designers can quickly produce engineering graphics by computer.In the current network environment,the 2D CAD engineering graphics are easily pirated in network transmission,and the legitimate rights and interests of copyright owners cannot be guaranteed.In addition,in the construction process,2D engineering graphics need to be printed into paper documents,which also provides an opportunity for lawless elements.At present,when digital watermarking is applied to copyright protection,it can embed authentication information into the carrier without people's awareness,which is effective at a low cost.Therefore,it is of great application value to carry out research on the key technologies of watermarking for engineering graphicsThis paper first introduces the research background and significance of the watermarking technology of engineering graphics,expounds the research status of 2D vector graphic reversible watermarking technology and the print-scan resilient binary engineering images watermarking,analyzes the shortcomings of the existing work,and summarizes the main research work of this paper.Second,the basic theoretical knowledge of digital watermarking is described systematically,including the concept and framework,the classification and the standard of performance evaluation.Finally,a reversible watermarking based on triple difference expansion and reverible contrast mapping is proposed for the copyright protection of 2D CAD graphics;In view of the copyright protection and traceability of engineering drawing,an automatic correction algorithm base on morphology and grid construction is proposed,which is suitable for digital restoration of print-scanned images.In addition,a pint-scan resilient watermarking for binary engineering images is proposed.The main work of this paper includes:(1)A reversible watermarking based on triple differences expansion and reversible contrast mapping is proposed in this paper.By establishing a new coordinates system,relative coordinates are constructed as cover data.The differences of every two adjacent relative coordinates are classified into 4 categories according to their values,and the watermark is embedded into the relative coordinates by using triple differences expansion and reversible contrast mapping.Experimental results and analysis indicate that the proposed watermarking significantly improves the capacity,imperceptibility,and it is robust against translation,rotation and scaling.(2)An automatic correction algorithm for binary engineering images is proposed.The border equation is fitted,and the grids is constructed according to it.Then,the image is restored by the ratio of black and white pixels in grids.When the image is too large to bring offset,it necessary to print the correction image,which is used to generate the offset coefficient table,and then apply the rule to the image correction.Experimental results show that the proposed algorithm can effectively restore the print-scanned image.(3)A print-scan binary engineering image watermarking based on quantization and pixel addition is proposed.First,the line segment in the image is identified as the watermark embedding area,and the watermark sequence is divided into groups.Second,for every watermark group,a reference pixel block is added according its group number,and the quantization intervals is calculated.Finally,watermark is embedded by adding pixel blocks at corresponding position in the quantization intervals.Watermark can be extract directly by identifying watermark pixels,without reducing the image.The experimental results show that this algorithm can effectively resist print-scan and photocopy attack,and it has large capacity,good imperceptibility,and a wide application foreground.The research results of this paper can be applied to the copyright protection and traceability of engineering graphics,and provides new and effective methods for the safety protection of engineering graphics.