A reversible and visible watermarking algorithm which has superior performance on robustness and real-time is designed to protect the copyright of electronic scanning for libraries,museums.Firstly,every original image is one page of electronic picture and binary image is made as watermark.The chosen embedding areas of original image are made color space conversion to get Y component,which is applying NSCT with two levels on them to get low and high frequency sub-bands.Each frequency sub-bands of watermark image is embedded into the corresponded low and high sub-bands of selected area of original image with different adjustment coefficients.Then,Rijndael algorithm is used to encrypt and decrypt in document pictures.The system can remove the visible watermark from watermarked document image for only the authorized user,so that user can download the encrypted one and decrypt it on the register terminal.The study is helpful to the protection of electric scanning for libraries,museums.%设计了一种鲁棒性和实时性兼具的可逆可见水印算法,以保护大量馆藏珍贵图书电子文档的版权.首先,将电子文档的扫描图像作为载体图像,二值图片作为水印图像.在载体图像上选择嵌入区域,将该区域进行颜色空间转换得Y分量,对Y分量进行2级非下采样Contourlet变换,对得到的高频子带和低频子带分别按照不同的嵌入强度进行水印嵌入,经过一系列逆变换得到含水印图像.其次,使用Rijndael算法完成电子文档的加解密.最终,系统能为授权用户清除水印并提供加密的高清版本下载,用户在注册终端可自动解密文档.有助于网络环境下电子文献资源的版权保护,促进馆藏数字信息资源的共享,很好地解决了电子文档的流通与版权保护之间的矛盾.
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