基于离散余弦变换的三维点云模型全息盲水印

目的 为保护三维模型版权， 提出一种基于离散余弦变换的三维点云模型全息盲水印算法。方法 对三维点云模型进行仿射不变性处理， 将三维模型由直角坐标系转到球坐标系， 并对球坐标中的角度值进行升序排序； 将顶点到质心的距离按顺序存入64×64的数组中， 作为水印嵌入对象； 二值水印图像经全息水印技术生成全息水印， 并对全息水印进行分块离散余弦变换， 在该变换域的中频部分实现对水印的嵌入， 再经过离散余弦逆变换， 实现由频域到空间域的变换， 生成带有水印的三维模型。结果 提出的算法是一种盲水印算法， 对一些仿射攻击具有较好的鲁棒性。将水印嵌在变换域的中频部分， 水印的不可见性及稳定性增强。结论 提出算法可成功获得水印信息， 采用全息技术实现了三维模型版权保护。

Holographic Digital Blind Watermark Algorithm for 3D Point Cloud Model Based on Discrete Cosine Transform

In order to protect copyright of 3D model, this paper present a kind of algorithm of holographic digital blind watermark for 3D point cloud model based on discrete cosine transform. Firstly, affine invariant preprocessing was used for the 3D model. Then, coordinates of the 3D model were switched to spherical coordinates with the angle value in an ascending sort order. The distance from the object center to the vertices was taken as the watermark embedding object to embed the watermark in the 64 × 64 array. Holographic watermarking technology turned binary watermark image into holographic watermark. By discrete cosine transform, the intermediate frequency part of holographic watermark was embedded with the watermark through inverse discrete cosine transform to realize the transformation from the frequency domain to the spatial domain. The proposed algorithm belonged to blind watermark and had the high performance of the watermark robustness. Also, the performance of invisibility and stability was enhanced because the watermark was embedded in the intermediate frequency part. The algorithm can obtain the watermark from the 3D model successfully, and also the holographic watermarking technology can protect copyright of 3D model better.