软判决检测的鲁棒图像水印方案

数字水印技术是现代版权保护的手段之一,而数字水印系统的鲁棒性是其能够起到版权保护作用的必要条件,也是当前的研究热点。本文提出了一种Turbo编码的图像水印的软判决检测算法,在不改变原有的嵌入算法的前提下,只需在接收端采用软判决检测算法就能有效地提高水印系统的鲁棒性。在本文提出的方案中,首先把原始水印信息进行Turbo编码,在图像DFT变换域中,修改两个相同频点系数的大小关系来嵌入经过编码的水印信息。在检测水印时,采取软判决检测算法提取用于Turbo译码的软输入信息,可有效地提高系统的鲁棒性。实验结果表明,软判决检测的比特错误率普遍低于硬判决检测的比特错误率,在高斯噪声情况下,甚至能低0.169。

Soft-decision Detection Robust Image Watermarking Scheme

Digital watermarking technology is one of the means of copyright protection. Robustness of a digital watermarking system is a necessity to protect digital works' copyrights, and it is the hot spot of research at present. In this paper, a soft detection algorithm for Turbo-coded robust image watermarking scheme is proposed. Robustness of a watermarking system is improved without any change to watermark embedding when we apply the soft detection algorithm at the receiving end. Watermark information is encoded by Turbo-codes firstly and then is embedded into the original image in the DFT domain. For each bit of the coded information, a pair of points with the same frequency is pseudo-randomly selected and modified. During watermark detection, softinput messages for Turbo decoding are collected by adopting the soft-decision detection algorithm, which improves the robustness of the watermarking system effectively. Experimental results indicate that the Bit Error Rate (BER) of soft-decision detection femains lower than that of hard-decision detection, even 0.169 lower in gaussian noises.