一种抵抗几何变换攻击的数字图像水印方法

在水印嵌入的过程中，首先在原图像经过对数极坐标变换后的图像中寻找水印嵌入的特定区域，并在该特定区域所映射的原图像经过离散傅立叶变换后的图像区域中随机选择像素点嵌入水印，保证了水印嵌入位置的不重复和不可侦测性。在水印提取的过程中，提出了获得图像旋转角度与缩放比例的方法，简化了水印的提取过程。实验证明，将对数极坐标变换和离散傅离叶变换结合后，在图像指定区域选择随机嵌入点嵌入的水印对于几何攻击具有良好的鲁棒性。

Robust Digital Image Watermarking Method Against RST Attacks

Digital watermarking on images is a key technique for pr otecting copyright of images. Many digital watermarks for images are sensitive t o geometric distortions, such as simple rotation, scaling, and/or translation(R ST) attacks. It is an effective way to embed watermark using log-polar transfor m(LPT) and discrete Fourier transform (DFT) against RST attacks. During watermar k embedding process, this paper first uses LPT of original image to find the spe cific area which is selected to embed watermark, then maps this area to the DFT of original image. Embed watermark randomly in pixels of the mapped area in DFT of original image ensures that the embedded watermark is security and undetecta ble by attackers. During watermark extract process a method for detecting the ro tation angle and scale of digital image is used to simplify the extract process. Experimental results indicate the feasibility and effectiveness of the method a gainst RST attacks.