一种改进的小波系数差异量化水印算法

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,该算法能有效抵杭各种攻击,并且图像峰值信噪比可以保持在55dB左右。

Improved Watermarking Based on Significant Difference of Wavelet Coefficient Quantization

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 8 wavelet coefficients in a pseudorandom manner using a key. Then,1 bit 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. hhe experimental results show that the proposed scheme is quite effective against JPEG compression, low-pass filtering, Craussian noise and slight geometric attacks, and the PSNR of watermarked image is about 55dB.