抗几何变换的小波域自适应图像水印算法

小泼变换不具有几何不变性，因此，小渡域水印对抗几何攻击是一个十分困难和富有挑战性的课题。提出了一种抗几何变换的小波域自适应图像水印。此方法根据人眼视觉系统掩蔽特性，将水印自适应地嵌入DWT域的低频子带。并且通过在DFT中频区域一个圆环上嵌入模板以及对一个限定区域不变质心的提取，实现在水印检测前估算和校正图像所经历的几何变换。实验结果表明：该水印不仅具有较好的不可感知性，而且对诸如旋转、缩放、平移等几何变换和常规的图像处理具有较强鲁棒性。

Image-adaptive Watermarking Algorithm Robust to Geometric Distortion in DWT Domain

The wavelet transform has no ability to resist to geometric distortion,so the wavelet domain watermarking resisting to geometric distortion is a very difficult and challenging subject.A watermarking algorithm robust to geometric distortion in DWT domain is proposed.In the algorithm,a watermark was embedded adaptively in low band of DWT domain,according to the conceal quality of Human Visual System(HVS);Especially,the geometric transformation could be corrected before the watermarking detection,owing to embedding a template in a circle of middle frequency in DFT and extracting a invariant centroid from a restricted area inside the image.The experimental results show that the watermark is robust to geometric distortions and general image processing techniques.