提出了一种优化的基于离散小波变换（DWT）的抗打印扫描的数字水印算法。算法将小波系数分为低频、中频、高频3类，并根据人眼视觉系统对这3类系数的不同分辨率加载了不同强度的水印信息，在保证不可见性的前提下增加了鲁棒性；同时在提取时增加了对扫描图像预处理过程，提高了水印信息提取的正确率。实验证明，算法对剪切、噪声、压缩攻击都具有较好的鲁棒性。

An optimized watermark algorithm based on discrete wavelet transform (DWT) was put forward, which can resist to printing and scanning. The algorithm divides wavelet coefficients into low frequency, middle frequency, and high frequency. Watermark of different intensities was applied to guarantee invisibility and increases robustness according to different resolutions of human vision to the three coefficients. Pretreatment process was added while extracting scan image to enhance the extraction accuracy watermark information. Experiments showed that the algorithm has good robustness to shear, noise, compression attacks.