一种基于小波域的灰度水印逐层嵌入算法

Gradual gray-watermark embedding algorithm in the wavelet domain

提出了一种基于小波域的逐层嵌入灰度水印的方案。算法充分利用人类视觉系统(HVS)的掩盖效应,将水印图像数据分成比特平面组,并将每组的比特平面置乱后转化成一维水印序列。在小波域中按阈值逐层折半递减迭代,选择出适合嵌入水印的某几层,并随机搜索出每层中应嵌入水印的系数,将每个一维水印序列按重要性嵌入到相应层随机选出的系数中。同一系数可以重复嵌入水印,增大了嵌入容量。水印图像可以渐进式地恢复,达到一定的相似度时,可随时停止水印的提取。仿真实验表明该算法具有良好的稳健性和不可见性。

A gradual gray-watermarking embedding scheme based on the wavelet transform was proposed in this paper. It made full use of the invisibility of the Human Vision System （HVS） in the algorithm. The watermarking digitals were divided into bits plane. Every bits plane were permuted and converted into 1-D array. As the value gradually decreased by half from layer to layer in the wavelet domain, all important coefficients of each layer were randomly searched, the 1-D array watermark compared by the bit plane was embedded into the corresponding layer＇s importance coefficients according to the watermark＇s importance. The same coefficient can be embedded by watermark repeatedly, so as to enlarge the embedding capacity. The watermark picture can be reconstructed gradually. When achieving certain degree of similarity, we can stop withdrawing watermark from the picture which was embedded by watermarking at any time. Experimental results show that this algorithm is of good invisibility and robustness.