为了设计更加鲁棒的数字水印算法，在对水印的嵌入过程、提取过程及其抗攻击性能进行分析的基础上，提出了一种图像灰度水印自适应嵌入与自适应提取新方案。该方案基于小波变换的多分辨率特性，利用人眼的亮度感觉及对比灵敏度阈值等人类视觉系统特性，并结合图像各个局部小波子块的亮度与纹理特征，在嵌入的过程中，通过动态地计算各个局部块的自适应嵌入强度因子来嵌入水印。提取时，则根据从不同区域提取出的水印信息自适应计算最佳的水印提取结果，这就从提取的角度大大改善了水印系统的性能。实验结果表明，该算法对多种攻击具有较强的鲁棒性，尤其对平滑、滤波、JPEG压缩、JPEG2000压缩以及位平面去除等攻击，其鲁棒性更明显。

In order to design an image watermarking algorithm with high robustness, through the analysis of watermark embedding process, extracting process and performance, this paper presents a new scheme of Image adaptive Gray-scale Watermark Embedding and Extracting. After analyzing the characteristics of multiresolution of the two-dimension discrete wavelet transform, by using luminance sense and contrast sensitivity threshold of the Human Visual System and integrating the luminance and texture characteristic of each sub block of the image, the scheme embeds a gray-scale watermark into a host image according to the adaptive embedding intensity factor calculated. The optimal watermark extracting result can be calculated adaptively according to the watermark information extracted from different regions, which greatly improves the performance of the watermark system. The experimental results prove that the scheme is robust enough to many attacks, especially to smoothing, filtering, JPEG or JPEG2000 compression and bit plane cutting.