针对2维CAD工程图对高精度的要求，提出一种采用改进量化索引调制（IQIM）的2维CAD工程图小波域可逆水印算法。该算法首先提取2维CAD工程图中所有实体的顶点信息，并对顶点信息依次进行顶点变换和离散小波变换以获取仿射变换不变性，然后使用改进的量化索引调制算法将加密后的水印信息嵌入到所有的细节系数中。实验结果表明，该算法具有良好的可逆性、不可见性和较大的水印容量，且对图形平移、旋转、均匀缩放等攻击具备较好的鲁棒性。

Since 2D CAD engineering graphics require high precision, a wavelet domain based reversible watermarking algorithm for 2-Dimensional CAD engineering graphics by using improved quantization index modulation (IQIM) is proposed in this paper. First, all vertices in the 2D CAD engineering graphics are extracted, and then Log-polar Mapping and discrete wavelet transform are done to them respectively to achieve the invariance of affine transform. Finally, the encrypted watermark is embedded into detailed coefficients by using improved quantization index modulation (IQIM) scheme. Experimental result shows that the proposed algorithm has a large capacity, good invisibility, and robust against the attacks such as transformation, rotation, equal scaling etc.