Gradual gray-watermark embedding algorithm in the wavelet domain
一种基于小波域的灰度水印逐层嵌入算法

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.