Abstract: To protect the copyright of large raster maps, a fast robust digital image watermark algorithm is proposed. With the blocking idea, the watermark is embedded into the Fourier semicircle region. When the watermark is extracted, the watermarked image is first preprocessed, and then the spectrum is mapped to standard size with neighbor averaging method, which assures blind extraction, and resolves the problem caused by block-image embedding as well as whole-image extraction. Experimental results show that the algorithm has the advantages of low memory requirements, high efficiency performance and robust for attacks of cropping, rotation, contrast and light variation.

Key words: semicircle, blind watermark, image cropping

摘要： 为解决大数据量栅格地图的版权保护问题，提出一种快速、鲁棒的水印算法。该算法基于分块思想将水印嵌入到傅立叶频域的半圆形区域。在提取水印时，先进行预处理校正，再利用邻域均值法将大幅面图像的频谱图映射成为标准大小的频谱图，既做到了盲提取，又解决了分块嵌入与全图提取带来的问题。实验表明该算法占用内存小、运行效率高，对裁剪、旋转、对比度和亮度变化等攻击具有较好的鲁棒性。

关键词: 半圆, 盲水印, 图像裁剪

CLC Number: 

• TP301.6