一种新的基于内容的公开水印技术

A Public Watermarking Algorithm Based on Image Content

提出了一种新的基于内容的DCT域公开水印算法。通过调整Hilbert块索引序列两相邻分块中对应的中频系数的大小关系．将水印嵌入原始图像。实验表明，该技术充分考虑了人类视觉系统的屏蔽特性，嵌入水印与原始图像是自适应的．能较好的保证水印的不可觉察性；同时对常见的信号处理技术以及剪切、旋转与缩放等几何变换具有鲁棒性，尤其对锐化、对比度增强；边缘增强和直方图均衡等信号增强处理具有的鲁棒性更为可观。

A content based image public watermarking algorithm which operates in DCT domain is proposed in this paper. Two neighboring sub-blocks in the Hilbert sequence is pseudo-randomly selected by using chaotic sequences. Then a watermark with visually recognizable pattern is embedded into the original image by changing the polarity of the corresponding middle-frequency coefficients in the two chosen neighboring sub-blocks, and the watermark is adapted to the image by exploiting the masking characteristics of the human visual system （HVS）, thus ensuring the watermark invisibility, and the watermark don＇t need the original image. The experimental results show that the proposed algorithm in this paper is robust to common signal processing techniques and some geometric distortions, such as cropping, scaling and rotation. Especially, it achieves high robustness under signal enhancement operations, such as sharpening, contrast enhancement, edge enhancement and histogram equalization.