一种抗几何攻击的数字水印算法

文中提出了一种基于对象的抗几何攻击数字水印的方法，将水印嵌入到图像中的对象部分而非整幅图像，并利用自参考函数实现抵抗RST变换等各种几何攻击。首先对原始图像进行边缘检测以提取出对象，然后用边界跟踪算法选择嵌入区。然后把要嵌入的水印信号作预处理及周期化，并自适应的嵌入到选择好的嵌入区间中。水印提取时估计出受攻击之后的水印，并用ACF函数判断图像所经历的几何变换，以得到正确的水印信息。实验表明对几何攻击及JPEG压缩都有较好的鲁棒性。

A Digital Watermarking Algorithm Resistant to Geometrical Transform

This paper proposes an affine-resistant digital image watermarking algorithm based on object, which embeds the watermark in the object instead of in the whole picture. And the autocorrelation function is used to resist geometrical transformation. First, the edge detection is used to extract the object from the original picture, then the boundary tracking algorithm is employed to choose the embed area, then to pre-process and periodize the watermark, and then to embed the watermark in the chosen area adaptively. In the extraction phase, the attacked watermark is first estimated, then the autocorrelation function is used to estimate the geometrical transformation undergone by the picture. The experimental results indicate that this technique have a good performance for geometrical attacks and JPEG compression.