目的 结合四元数和全息技术的优势， 将数字水印技术应用在彩色图像中， 以提高水印算法的抗攻击能力。方法 将四元数离散傅里叶变换和加密傅里叶全息技术应用到数字水印算法。首先对一幅彩色图像进行数据类型的转换， 表示成四元数矩阵， 然后对其进行四元数离散傅里叶变换， 最后基于人眼视觉特性将水印信息加密后利用重复计算选取合适的嵌入强度后嵌入变换得到的频域矩阵中， 实现信息隐藏。结果 算法能够将彩色图像作为一个整体进行处理， 有较好的不可见性。与此同时， 提高了四元数域水印对于裁切攻击的抵抗能力。结论 该算法在保证水印不可见性的同时能够抵抗一定程度的攻击， 满足数字防伪以及版权保护的需要。

A new method based on the advantages of quaternion and encrypted Fourier holography was put forward to improve the robustness against attacks and it was used for color image watermark embedding and extraction. The quaternion discrete Fourier transform and encrypted Fourier holography were applied in digital watermark algorithm. At first, the color image was represented in the form of quaternion matrix by translating the data type, and then subjected to quaternion discrete Fourier transform. At last, the hologram was embedded into frequency matrix with an appropriate coefficient which was obtained by repeated calculation on the basis of human visual system. The experiments showed that the method had good performance in invisibility and disposed the host color image as a whole. Meanwhile, it also improved the robustness against cut attacks in quaternion domain watermarking. The watermarking algorithm met the demand of invisibility and robustness and was effective in digital anti-counterfeiting and copyright protection.