基于图像特征点的数字水印算法

Digital watermarking algorithm based on image feature point

几何攻击作用在加载有水印的图像上,水印同步信息被破坏,导致水印检测失败。为了恢复已失去的同步信息,提出一种基于筛选尺度不变特征估计几何攻击参数的数字水印算法。首先提取图像的尺度不变特征,利用像素差的平方和筛选尺度不变特征,去除易受几何攻击影响的尺度不变特征,保证最小二乘法迭代运算快速收敛,迭代一次就能得到基本准确的几何变换参量;水印信息进行游程编码,在其码值对应的载体图像的DCT块内嵌入。实验结果表明,该算法能获得很好的图像质量,且能十分有效地抵抗各种几何攻击。

It might fail to detect watermarking now that geometric attacks perform on a watermarked image and destroy the synchronization of the watermark signals embedded in the image.To restore the lost synchronism,a novel method to estimate the geometric operation using sifted Scale-Invariant Feature Transform（SIFT）was proposed.According to Sum of Squared Differences（SSD）of the pixels,the suitable feature points were refined to ensure robustness of the least-squares solution.The least squares iterative was convergent quickly,and the one step iteration would be able to get high accuracy geometric parameters;encoding binary watermark image by using Run-Length Code（RLC）,watermarking was done by altering the coefficients of the DCT blocks corresponding to the value of RLC.The simulation results show that the proposed scheme achieves good image quality and it is robust to geometric attacks.