数字水印是一种嵌入到图象，视频或音频数据中的不可见标志，可以用于多媒体数字的版权保护，认证和标注等，为了提高在频率域嵌入水印抵抗裁剪攻击的能力，提出一种局部化的图象数字水印算法，该算法利用图象中相对稳定的特征点标示水印嵌入的位置，并在与每个特征点对应的局部区域中独立地嵌入水印，这样，当只有部分图象时，仍能通过这些特下点来定位并提取水印，此算法中，水印的嵌入是在局部图象的小波域中进行的，并采用对小波系数进行特殊量化的方法来隐藏水印比特，而水印的提取不需要原始图象参与，实验结果证明，算法对裁剪有很强的抵抗能力，同时对压缩，滤波，噪声，StirMark攻击等也有较好的鲁棒性。

A digital watermark is an invisible mark embedded in digital images, video or audio documents, which may be used for a number of different purposes including copyright protection, authentication and captioning. In this paper, we proposed a watermarking scheme that embeds watermarks in the local region of the image. This new idea that we name it local watermarking scheme, inserts watermarks into the wavelet domain of local regions of the image instead of entire image. We select some stable feature points in the image, and then use these points to identify the locations where we insert watermarks. When the image is cropped, the feature points in the remaining piece of the image will not change. We can extract watermark with the help of the remaining feature points. A special quantization procedure is used when we embed watermark bits into the wavelet coefficients of the sub image, and the watermark can be detected without knowing the original image. Experimental results show that the watermark scheme proposed in this paper is robust to cropping, and also has good robustness to compression, filtering, noise adding, and StirMark attack.