中文摘要：

提出了一种基于实体替换与小波均值的二维工程图盲水印算法.首先在保证工程图外观不变的情况下,将二维工程图中的直线替换成多段线,并提取多段线顶点坐标进行变换以获取旋转、平移和缩放不变性,然后对变换后的顶点坐标数据构造变换单元,对每个单元进行二维小波变换,最后在小波系数中嵌入水印.同时对水印信息采用混沌加密以提高水印的安全性.实验结果与分析表明：这种算法能够实现水印的盲提取,具有良好的不可见性和较高的运行效率,并对平移、旋转、均匀缩放、图形增加等攻击具有良好的鲁棒性,为二维CAD工程图的版权保护提供了一种新的方法.

英文摘要：

A blind watermarking algorithm for 2D engineering graphics based on entity substitution and mean value of wavelet coefficients is proposed.Firstly,each line entity of the 2D engineering graphic is substituted by a polyline with k＋1 vertices,and the substitution will not change the appearance of the 2D engineering graphic.Then the coordinates of the vertices in polylines are acquired to make some transformations to obtain the invariant abilities such as translation,scaling and rotation.After that,the coordinates of the transformed vertices are constructed into different transformation units.Finally,the discrete wavelet transformation is done to every transformation unit,and watermark is embedded to the mean value of wavelet coefficients of each transformation unit.Meanwhile,chaotic encryption and chaotic decryption are also used in the watermark embedding and watermark extraction,respectively,to improve the security of the watermark algorithm.Experimental results and analysis show that the proposed algorithm is blind detection,and it has a good capability of imperceptibility and has a high efficiency.At the same time,it is robust to the attacks such as rotation,translation,even scaling and graphic addition.It may be a potential new method for the copyright protection for the 2D CAD engineering graphics.