一种改进的小波系数差异量化水印算法

Improved Watermarking Based on Significant Difference of Wavelet Coefficient Quantization

针对Lin等提出的"基于小波系数差异化量化"(SDQ)的水印方法存在的问题,提出了一种改进的小波系数差异量化水印算法。算法在密钥的控制下,伪随机地选择中频子带中的两块共8个系数组成一组,嵌入1bit水印信息,显著提高了SDQ算法的安全性。算法改进了SDQ的差异量化方式,在保持图像原有的重要系数大小关系的基础上,通过对最大系数进行小幅度的量化来加强差异,进而提高鲁棒性,并通过差异信息和水印信息生成密钥来提取水印。实验结果表明,该算法能有效抵抗各种攻击,并且图像峰值信噪比可以保持在55dB左右。

In this paper an improved SDQ watermarking scheme was developed based on＂Significant Difference of Wavelet coefficient Quantization＂（SDQ）by Lin et al.Firstly,two blocks of the middle frequency band in DWT were divided into a group of 8wavelet coefficients in a pseudorandom manner using a key.Then,1bit watermark information was embedded in a group.The important coefficients difference was enhanced through slight quantization of the maximum coefficient,and the robustness was improved.Watermark was extracted by a secret key generated by coefficients difference and watermark.The experimental results show that the proposed scheme is quite effective against JPEG compression,low-pass filtering,Gaussian noise and slight geometric attacks,and the PSNR of watermarked image is about 55dB.