为了提高水印抗剪裁攻击的鲁棒性,提出了一种基于特征的方法,用来辅助决定水印的嵌入和提取的位置,并根据人类视觉的掩蔽特性,在较复杂的块增加嵌入量,而在DCT域的中低频带嵌入二值图像水印,并通过标志位的嵌入来辅助水印的提取,该算法除了对JPEG、模糊等图像操作具有很好的抵抗能力外,同时对裁剪也具有很好的鲁棒性。目前在许多水印嵌入算法中,当对剪切图像进行水印提取时,图像的大小和像素相对坐标均未发生改变;而本文对剪裁后的图像所进行的水印提取则是在图像的大小和像素的相对坐标均是未知的情况下进行的。实验结果证明,该算法是一种行之有效的盲水印算法。

As an effective technique of copyright protection,digital watermarking techniques have become a new focus of interest in recent years.A useful watermark scheme should be visually imperceptible and must be robust to various attacks.In this paper,a feature-based algorithm is proposed,which embedded a binary image as watermark in DCT domain by taking into account the feature of gradient and intensity of each block.Especially we embed marker bits to locate the original block of cropped image.The proposed technique could actually survive several kinds of image processing such as image cropping,shifting,blurring,noise,sharpening and JPEG lossy compression etc.The algorithm doesn't need the original image for watermark extraction and the simulation results prove its effectiveness.