基于人类视觉系统和离散小波变换的彩色图像水印

为了扩大数字水印的适用范围，提出一种基于人类视觉系统（HVS）和离散小波变换(DWT)的彩色图像数字水印算法。首先利用混沌加密算法把一个有意义的二值图像加密成水印;然后将彩色图像从RGB色彩空间转换到YCbCr空间，提取Y分量，对Y分量进行一级离散小波变换；最后求出低频分量LL1的视觉掩蔽值，根据视觉掩蔽值，将水印嵌入到彩色图像的Y分量的低频小波系数域上。实验结果表明，该算法具有较好的不可见性和鲁棒性。与以往的基于YCbCr颜色空间的算法相比，该算法具有更好的不可见性和鲁棒性。

Color image watermarking based on human visual system and discrete wavelet transform

In order to extend the range of applying of digital watermarks,this paper introduced a watermarking algorithm for color image based on Human Visual System (HVS) and Discrete Wavelet Transform (DWT). First, a meaningful binary image was encrypted by chaotic encryption algorithm to form watermark. Then the color image was converted from RGB color space to YCbCr space; the Y component was extracted and one level discrete wavelet transform was executed. Finally, the visual masking value of LL1 was got. According to the visual masking value, the watermark was embedded into the low-frequency wavelet coefficient domains of Y components of color image. Experimental results show that the proposed algorithm has better invisibility and robustness than the algorithm based on YCbCr color space.