基于格的灰度级水印技术

提出一个新的灰度级水印算法．首先，使用量化技术对灰度级水印进行预处理，实现灰度级水印的数据压缩；然后，对原始图像进行小波分解，在小波域中使用格矢量量化技术构造水印的嵌人和提取算法．提取水印不需要原图像．为增强水印的安全性，使用混沌序列作为密钥对水印序列进行调制．实验结果表明，与同类算法相比该算法在获得较好感知质量含水印图像的同时提高了水印的鲁棒性．

Lattice Based Gray-Level Digital Watermarking

A novel gray-level digital watermarking is proposed. It uses grayscale image instead of binary image as the watermark. The watermark image is decomposed using two layer wavelet transformation and a simple quantization technique is used to further decompose the coefficients into bit sequences. After original image is decomposed using three layer wavelet transformation, the lattice vector quantization is used to construct the embedding strategy, in which coarse and detail watermark sequences are embedded into coarse and detail coefficients of original image, and the extracting strategy without need original image. To enhance security of the watermark, chaotic sequence is used to modulate the watermark. Experiment results have demonstrated that the proposed algorithm is more robust against JPEG compression and additive white gaussian noise than other similar watermarking algorithm, while the watermarked images have better quality. The recovered watermark image has good quality even under JPEG compression with a quality factor of 30.