随着因特网和数字技术的发展,数字媒体已成为人们获取知识的主要手段,但这也带来了一系列问题如作品侵权、非法复制和传播等.为了解决这些问题,数字水印技术作为版权保护的重要手段,已得到广泛的研究和应用.为实现水印图象的叠加,提出了一种以灰度图象为水印的空域二维自适应数字水印算法,该方法首先将水印图象进行8×8分块,并进行DCT变换,然后对每块的DCT系数进行量化和调整,最后,取出每块的部分DCT系数来构成水印信号.同时为了实现自适应,还将载体图象按8×8分块,并利用视觉掩蔽特性对载体图象象素进行分类,再根据块分类结果,将水印信号以不同强度嵌入到载体图象中.实验结果表明,该算法具有较好的鲁棒性.最后还对该技术今后的研究指出了一些可能的方向.

The digital media, including text, image, graphics, audio and video etc., has become a main way for information communication along with the popularization of Internet and the development of multimedia techniques. People can get almost information through the Internet. But this gives rise to serious problems including wide spread copyright violation, illegal copying, easy forging etc. How to provide copyright protection has drawn extensive attention in recent years. As a main method for copyright protection, the techniques of watermarking, have been widely studied and applied. In this paper, we proposes an adaptive 2 dimension image watermarking algorithm in space domain with gray image's watermark. In order to embed the image's watermark, we split the image's watermark into blocks and transform them into DCT domain. Then quantize their DCT coefficients and adjust them. Finally, take out the parts of DCT coefficients from each block to constitute the watermark. By using the human visual system, we split the original image into blocks and classify them. According to the classification, the watermark components with different strength are embedded into cover image. The experimental results show our algorithm has very excellent effect. Finally, we make a discussion on some open problems and point out possible directions for further research.