用多数字基整数实现小波域多重数字水印嵌入

提出多数字基整数嵌入多重水印信息的算法。该算法基于人类视觉系统的掩盖效应的研究，利用小波域临界可见误差（UND）门限，决定水印嵌入的位置和动态调节水印嵌入的强度，从而使原始图像的小波系数加入水印的强度精确控制在门限内。多数子字基整数巧妙地将水印小波系数的信息转换为修改一组宿主图像小波系数的值。文中理论估计了该算法嵌入水印的容量，并分析了嵌入多重数字水印的可能性。该算法具有明显的优点：多个水印能够成功地嵌入版板保护图像；加水印图像没有改变时各个水印能完全恢复；对加水印图像进行攻击时，提取的各个水印图像清晰度高。实验结果表明，该算法很好地折衷了数字水印抵抗图像压缩、图像剪切等图像处理的鲁棒性以及数字水印不可察觉的矛盾，是一种很有前途的数字水印技术。

Multiple Digital Watermarks Embedding in Wavelet Domain with Multiple-Based Number

Based on the visual masking effect of human visual system, just noticeable difference (JND) thresholds in wavelet domain are used to precisely determine the locations for watermarks embedding and dynamically control the watermark's strength without exceeding the thresholds. A multiple based number system is proposed to skillfully convert the watermarks information into values to be embedded in the chosen wavelet coefficients of the owner image. This paper evaluates the capacity of the watermarking method in theory and also analyzes the possibility of inserting multiple watermarks into the owner image. It is shown with experimental results that a good tradeoff between transparency to human eye and robustness of image processing including image compression, image cropping etc is guaranteed in this method.