Abstract: In this paper，two robust digital watermarking algorithms based on image normalization and invariant centroid theory are proposed.In order to boost up the safety and the solidity of the watermark，it is scrambled and chaotically encrypted before embedded into the original image.Firstly，both of the two methods use image normalization and the invariant centroid theory to obtain its significant region from the normalized image，then the scrambling watermark images are embedded into the significant regions.Experimental results show that the two schemes are invisible and robust against geometric attacks，especially each scheme has its own advantages.

摘要： 以图像归一化和不变质心理论为基础提出了两种安全性较高的数字图像水印算法。为了增加水印的隐秘性及抗干扰能力，水印在嵌入前均进行了置乱和混沌加密处理，然后两种方案分别根据其归一化图像的不变质心确定出相应的重要区域，并在该区域实施水印的嵌入。实验结果表明，提出的两种数字图像水印算法均具有较好的不可感知性和抗攻击的鲁棒性，且在抵抗常规信号处理和几何攻击下各具优势。