基于小波变换的图象水印嵌入方法

Image Watermarking Method Based on Wavelet Transform

数字水印技术作为数字产品版权保护的一项新技术 ,已受到越来越多的关注 .为保证水印的安全性 ,提出了一种基于小波变换的水印嵌入方法 ,即在嵌入之前先对水印做置乱处理 ,然后根据小波变换后 ,高、低频分量的特点 ,在高频部分嵌入较多的水印信息 ,而在低频部分嵌入较少的信息 ,亦即利用小波变换的层次结构 ,将同一水印反复嵌入到不同的位置 .实验证明 ,该方法对剪裁、JPEG压缩和锐化等图象退化处理均具有一定的抵抗力 ,是一种行之有效的水印嵌入方法 .

As a new technique applying to protecting the copyright of digital productions, the digital watermark technique has drawn extensive attention. A method of embedding the watermark in digital images based on the discrete wavelet transform is proposed. The watermark used here is not the conventional patterns such as a pseudo-random sequence or a bit stream but a text watermark. The information which the text watermark contains is abundant and intuitionistic, also the watermark is robust. To ensure the security of the watermark and make the watermark be hard to be extracted, the watermark is scrambled with Arnold scrambling transformation before embedded into the original image. According to the different characteristics of the high and the low frequency components of the wavelet coefficients of the original image, more watermark information is embedded in the high frequency components while less information in the low ones. That is to say, by using the hierarchical structure of the wavelet, the watermark is repeatedly embedded in various places. Moreover, experimental results have proved that the method is robust enough to some image degradation process such as cropping, JPEG compression and sharpening etc. So it is effective.