一种互补的栅格数字地图水印算法

针对栅格数字地图的版权保护，提出一种互补的栅格数字地图水印算法.该算法利用栅格地图相比自然图像具有较高亮度，直流分量变化比较大的特点，分别将水印嵌入到地图离散余弦变换后的直流分量和高频分量.直流分量部分依据亮度控制调制幅值嵌入水印，高频部分依据高频系数分段求和的奇偶性嵌入水印.在依据几何特征对地图预校准后，按嵌入的逆过程分别提取水印，并在合成系数控制下合成水印信息.实验结果表明，所提出的互补水印算法能够抵抗各种常见的恶意攻击，具有较强的鲁棒性

Complementary watermarking algorithm for digital grid map

To protect copyright of digital raster map,a complementary watermarking algorithm was proposed based on digital raster map.The characters of raster map with higher luminance and greater variation than natural image were utilized.The watermark was embedded respectively into direct current section and high frequency section after map discrete cosine transform.When the watermark was embedded into the direct current section,the modulation amplitude was controlled according to the luminance.The watermark was embedded into the high frequency section through the parity in the sum of segmented high frequency coefficients.After pre-calibrating the map's geometry features,the watermark extraction processes were executed respectively by embedding watermarking reversely,and the watermark information was synthesized under the control of synthesis coefficients.The experimental results show that the complementary watermarking algorithm can withstand various malicious attacks,and has very strong robustness.