基于像素三元组的差值扩展可逆图像水印算法

一般差值扩展可逆水印算法通过图像像素对的差值扩展嵌入水印,最大嵌入率为0.5 bpp(bit per pixel),存在嵌入率低 和失真较大的问题。为了提高嵌入性能,提出基于像素三元组的差值扩展可逆图像水印算法 。 首先利用图像像素的相关性,通 过像素三元组均值局部方差选择平滑区域,然后扩展像素三元组中像素值与其均值差嵌入水 印。 另外,为了提高图像不可感知 性和防止嵌入水印导致像素值的溢出,嵌入水印时,设定阈值限制在平滑区域嵌入水印时像 素值的改变。本文提出的算法最 大嵌入率能到达0.66 bpp,比传统的差值扩展算法提高33%,实验结果表明提出的算 法能在 较高嵌入率时仍保持较大的峰值信噪比,有效地提高了水印嵌入容量和降低了图像的失真率。

Reversible watermarking algorithm using difference expansion based on pixel tern ary

General difference expansion algorithms embeds watermark by expanding difference between pixel pairs,and the maximum embedding rate is 0.5bpp.The disadvantages of these algorithms are low embedding rate and large distortion.In order to achieve higher embedding rate and better invisibility, a novel reversible waterm arking algorithm is proposed based on the differences expansion of pixel ternaries.The cover image is firstly divided into pixel tern aries,by utilizing the correlation of image pixels;the local variance of the pixel ternary mean is used to select the smooth region. Se condly,expand the differences between pixels and the mean of the pixel ternaries separately,and then embed one bit of secret data to the each expanded difference.The threshold is set to limit the change of pixel value when embedding watermark in the smooth region so as to improve the imperceptibility of the images and prevent pixel value overflow or under flow occurs.The maximum embedding rat e of the proposed algorithm reaches 0.66bpp, which is 33% higher than the conventional differential expansion algorithm.The experimental results show that the proposed algorithm can maintain a higher peak signal-to-noise ratio at a high embedding rate,effectively improve the watermark embedding capacity,and reducethe distortion rateof the image.