基于双混沌置乱和扩频调制的彩色图像盲水印算法

提出了一种新的适应彩色图像的盲水印算法,先对宿主图像的绿色分量以8×8像素分块进行离散余弦变换(DCT)变换,用logistic映射生成两个混沌序列,然后用混沌序列置乱加密二值水印图像,并用两个互不相关的伪随机序列扩频调制水印,最后将调制好的水印嵌入到DCT变换域的中频子带系数上,进行分块DCT反变换得到水印化图像.提取水印时,通过比较两个伪随机序列和水印化图像的相关性大小来提取水印,不需要原始图像的参与,为盲提取水印算法.实验结果证明本文算法能有效地抵抗JPEG压缩、加噪、剪切等常见攻击,绿色分量嵌入水印比红色和蓝色分量嵌入水印能更好地抵抗JPEG压缩的攻击.

Color Image Blind Watermark Algorithm Based on Double Chaotic Scrambling and Spread Spectrum Modulation

A new blind watermark algorithm for color image was proposed. First, the green component of the original image was blocked by size 8×8 pixels and transformed with discrete cosine transformation (DCT). Second, two chaotic sequences were generated by logistic mapping, and the binary watermark image was scrambled by the chaotic sequences and spread spectrum modulated by two uncorrelated random sequences. Third, the modulated watermark was embedded in mid-frequency region coefficients of DCT domain. At last, the watermarked image was obtained by inverse discrete cosine transform. The watermark was extracted by comparing the correlation between two random sequences with watermarked image, the process did not need the original image, namely a blind watermark algorithm. Experimental results demonstrated that this method is invisible and robust against some usual attacks such as JPEG compression, cropping, adding noise, and embedding watermark in green component is more robust against lossy compression than embedding watermark in red or blue component.