彩色图像四元数频域幅值调制水印算法

彩色图像处理常用的独立单通道方式在处理过程中不能体现各彩色通道间的光谱联系。针对彩色载体图像，提出了一种彩色图像四元数频域幅值调制水印算法。首先在空域中计算四元数表示的载体图像块不均匀度大小，从而对载体图像的单位小块进行自适应选取;接着对彩色载体图像进行四元数傅立叶变换，得到其频域矩阵;然后计算分块傅立叶直流位置上的四元数模值，将水印嵌入在模值中。仿真实验结果表明，该方法可以把水印带来的误差扩散到图像的红、绿、蓝3色的各个分量上，且对常见攻击具有较好的鲁棒性，实现了数字水印不可见性和鲁棒性的良好结合。

Watermarking Algorithm for Color Images Based on Quaternion Frequency Modulation

Separate channel technictues performed on color images have the disadvantage of less ability to show connection between each channel during image processing. A new method to process color images with quaternion Fouricr transform was put forward in this paper. Firstly, ununiformity of each unit quaternion block in host image was calculated to pick up the potential block adaptively. Secondly, frectuency matrix of host color image was obtained by using quaternion Fouricr transforms. After that, the water marks were embedded into the amplitude of AC coefficient. Experimental results show that the image distortions from the watermark are spread into the three channels of a color host image and the proposed watermarking algorithm realizes a better trade off between imperceptibility and robustness.