基于PSNR小波域量化调制水印嵌入方法的参数定量估算

量化步长是量化调制方法中的重要参量，但是目前无法定量计算。针对这个问题，以抖动量化调制方法为研究对象，以小波变换系数为量化系数，提出了基于峰值信噪比(PSNR)的量化步长定量估算方法。首先根据量化误差的分布情况给出了基于量化步长的量化误差定量估算方法，然后根据小波变换的性质推导出了量化步长、水印序列长度与PSNR之间的定量关系式。实验结果显示，量化步长取值相同时实验测得的PSNR值和定量关系式计算出的PSNR值基本一致，验证了推导的定量关系式。

Immunity digital watermarking algorithm based on reversible information hiding in wavelet domain

To overcome the drawback of the existing immunity watermarking algorithm that the original image cannot be recovered exactly, a new reversible watermarking algorithm in wavelet domain based on immune watermarking framework was proposed. The algorithm has large embedding capacity and can recover the original image exactly. Meanwhile, the algorithm used histogram shifting method of reversible watermarking to embed recovery vector for recovering the original image precisely. By using the block size in the wavelet transform, the amount of the peak-zero point pair and the round amount in the histogram shifting, 〖JP2〗the control factor in the algorithm could be selected to decide the embedding depth. Then the algorithm could generate publishing image which has large distortion but also kept the main information of the original image. The scrambling and encryption methods were used in the algorithm so that the invaders could not recover the original image correctly by brute-force method without authorized file. The experimental results show that the algorithm can not only obtain the publishing image which has big differences with the original one, but also can recover the exact image when security permission is released.