一种彩色图像DC系数的自适应水印算法

提出了一种新的彩色图像DC系数的自适应水印算法。该算法通过简单地分析DCT块的两个AC系数将像素块分类成平滑块、边缘块和纹理块,然后根据像素块的类型自适应设置水印的嵌入强度。并利用图像亚采样得到的4个子图像间的高度相关性,将1比特水印嵌入在4个子图像块中由密钥控制的两个块的DC系数上,获得了分散水印能量与增加安全性的目的,而水印能直接在像素域中进行盲提取。同时嵌水印在YIQ模型的Y分量和RGB的B分量上,并进行了两者的性能比较与分析。大量实验表明,提出的水印算法取得了很高的不可见性和鲁棒性,Y分量水印的性能优于B分量的。

Color Image Watermarking Adaptively in DC Coefficients

A new approach of watermarking adaptively in DC coefficients of color images is presented. The proposed algorithm uses two AC coefficients of DCT blocks to classify the pixel blocks into three different types, namely, smoothed, edged, and texture block. The strength of watermark is set adaptively according to the pixel block type. Four subimages from the original color image can be obtained with down sampling. These subimages are highly correlated. Take into consideration the correlationship.One bit watermark is embedded，in two DC coefficients which is selected from the subimages. The selection of DC coefficients is based on Key controlled random numbers so as to disperse the energy of watermark and win secure watermarking. Blind extraction of watermark can be performed directly on pixel domain. Whilst the watermark is inserted into both the luminance component in YIQ model and the blue channel in RGB model, and examine and compare their performances. Extensive experimental results demonstrate that the algorithm achieves the high robustness and good quality of watermarked image, and the performance of watermarking in Y component outperforms that of B component.