一种抗几何变换的图像盲水印算法

为解决在几何变换时水印无法检测的问题,提出了一种抗几何变换的图像盲水印算法.该算法基于傅立叶变换和对数极坐标变换,实现了可以提取有意义字符的抗几何变换的盲水印算法.在嵌入水印过程中,通过对原始图像进行傅立叶变换,并选择中频部分进行对数极坐标转换变换,然后进行傅立叶变换,将水印嵌入幅度谱矩阵中.在提取水印过程中,结合模板矫正来降低各种积累误差,进行相应的反变换,并用局部最大检测法来提取水印.实验表明,该算法具有较强的鲁棒性,对几何变换、裁剪、压缩、锐化和涂改等抵抗性较强.

Image watermarking algorithm resilient to geometrical transform

To implement robustness of geometrical transform, an geometrical transform resilient watermarking algorithm was proposed based on fast Fourier transform (FFT)and log polar map(LPM).During the process of watermarking embedment, Fourier transform method for was implemented original image.Some suitable part of the frequency domain was mapped to Log-Polar system. Fourier transform was taken for the mapped part and watermark was embedded into them. During the watermark extraction process, a template was adopted to correct the image-signed, and the corresponding inverse transforms was used to obtain the magnitude. Finally, the watermark was recovered by the local maximum method according to the encoding. The original image was not required for extracting the embedded marks in this algorithm.The experiments show that the algorithm is robust to rotation, scale and translation (RST), JPEG, cut and erase.