基于非抽样Contourlet变换的彩色图像数字水印算法

研究了小波变换和Contourlet变换的不足,利用非抽样Contourlet变换的多尺度性、多方向性以及平移不变性特征进行彩色图像数字水印.先对图像进行非抽样Contourlet变换得到不同尺度不同方向上的系数.然后为了满足水印的不町见性和稳健性,在低频系数和高频系数中采用不同的嵌入强度.并依据人类视觉的彩色感知特性,在蓝色分量中嵌入较多水印,在其他颜色分量选取变换系数能量最大的区域嵌入水印.与同样嵌入规则的Contourlet变换算法和平稳小波变换算法相比.该算法具有更好的稳健性,利用该算法得到的水印相似度更高,最高町提高约0.5.

An Algorithm for Color Image Digital Watermarking Using the Nonsubsampled Contourlet Transform

The disadvantages of wavelet transform and contourlet transform are studied. Color image digital watermarking is implemented based on the multi-scale, multi-direction, and shift-invariance of the nonsubsampled transform. The coefficients in different scales and directions are obtained by image decomposition using the nonsubsampled contourlet transform. Embedding intensities of the low and high frequency coefficients are different invisibility and robustness of watermark requirements for according to the color perception characteristics of human visual system, watermark embedded in blue channel is more than the others, which only choose the local of maximal energy to embed. Compared with the algorithms of stationary wavelet transform and contourlet transform under the same embedding rule, this algorithm is more robust, with higher similarity which can be improved by 0.5 at most.