一种新的基于DWT变换的图像水印算法

A Novel Image Watermarking Algorithm Based on DWT

基于小波变换,提出了一种新的灰度图像水印技术。首先将彩色图像映射为一幅灰度图像,对这幅灰度图像进行L级离散小波分解,并将每级小波系数分成四个系数集合,根据水印图像W同时对小波系数进行重新量化,然后进行L级小波重构,获得含有水印的灰度图像,根据该灰度图像改变原彩色图像,从而得到嵌有水印的彩色图像。提取水印时,也是先将彩色图像映射为一幅灰度图像并做小波变换,对水印的每一点郝选取Δ值最大的相应小波系数进行提取,得到水印图像W’。测试结果表明该技术具有良好的性能,可用于图像的版权保护。

A novel technique for the digital watermarking of still color images based on the discrete wavelet transform (DWT)is presented. Transform a host color image to a gray image firstly,then compute the Lth-level discrete wavelet decomposition of the gray image. Compartmentalize every level's wavelet coefficients as four sets ,with which the watermark W is embed simultaneously and do invert wavelet transform to obtain the watermarked gray image. Change the host color image based on the gray image to get the watermarked color image. When extract watermark, transform the color image to a gray image and do Lth-level discrete wavelet transform to the gray image,distill watermark data W' from the wavelet coefficients whose A value is maximal. Test results show the superior performance of the technique and potential for the watermarking of still image.