给定降质约束下一类DCT域图像水印算法的拉伸系数估计

Estimation of the Scaling Parameter for an Image Watermarking Algorithm in the DCT Domain According to the Assigned Image Degradation Grade

数字水印是数字作品版权保护的重要技术手段。与噪声污染类似,数字水印的嵌入必然会损失原作品的质量。数字图像的质量直接关系其商业价值,在给定降质约束下自适应地调节嵌入深度是符合产业化标准的数字水印关键技术之一。根据DCT交流系数的拉普拉斯分布模型,推导了DCT域典型水印算法中拉伸系数与信噪比和峰值信噪比之间的理论关系。依据该理论关系,得到了在给定降质约束下一类典型图像水印算法的拉伸系数估计方法,实验结果表明该估计方法具有较高的精度。

Digital watermarking is a key technique for protecting intellectual property of digital media. Similar to the noise pollution, watermarking process may induce image degradation. Since image quality is a determinant of its worth, it is significant to adjust the parameters in watermarking algorithm to satisfy Specified quality requirement. Based on the Laplacian distribution model of AC DCT coefficients, we deduce theoretical relationship between the scaling parameter in a typical watermarking algorithms and signal to noise ratio (SNR) or peak signal to noise ratio (PSNR) of watermarked images. Thus the scaling parameter can be estimated according to the assigned image degradation grade. Experimental results demonstrate that the estimation has enough accuracy.