一种新的半脆弱彩色图像数字水印算法

A New Semi-fragile Color Image Watermarking Algorithm

提出了一种基于内容的半脆弱彩色图像数字水印嵌入算法,该算法可同时用于彩色图像的版权保护和内容认证．首先将彩色载体图像从RGB空间转换到YCrCb空间．然后对亮度(Y)进行L+1级小波分解,并将分解后的小波近似系数用混沌序列进行调制从而生成基于图像内容的数字水印信号．最后对亮度(Y)及色差(Cr和Cb)进行L级小波分解,并结合视觉感知特性及局部系数相关特性,通过分块量化措施将水印信号嵌入到载体图像(Y、Cr和Cb)的小波域中．仿真实验表明,本文算法不仅具有较好的透明性,对JPEG压缩、叠加噪声、平滑滤波等常规图像处理操作具有较好的鲁棒性,而且能够对剪切、替换等恶意图像篡改作出报警并确定被篡改位置．同时常规图像处理下其误检率与漏检率均比较低．

A new content-based semi-fragile color image watermarking algorithm is proposed in this paper, which can be used for color image copyright protection and content authentication simultaneously. Firstly, the color image is converted from an RGB color space to a YCrCb color space. Secondly, the luminance component （Y） is decomposed by the L＋1 level discrete wavelet decomposition, and the approximate wavelet coefficient matrix of the luminance component （Y） and the chaotic sequences are used to generate the content-based and secure watermark. Finally, luminance component （Y） and chrominance components （Cr and Cb） are decomposed by the L level discrete wavelet decomposition, and the watermark is embedded into color components （Y, Cr and Cb） by using the technique based on human visual system and block quantization. Experimental results show that our semi-fragile watermarking scheme is invisible and is robust to common image processing （such as JPEG compression, noise adding, filtering）. The proposed watermarking algorithm is fragile to content modification （such as cropping）, can detect effectively the tampered regions, and has a lower probability of missing or false alarm, compared with other popular semi-fragile watermarking schemes.