基于奇偶校验的块误差分散半调水印算法

Halftone image watermarking with block-directed parity-matched error diffusion

提出了一种顽健的半调水印算法。算法通过比较像素块的均值和一个图像自相关阈值的大小确定像素块的奇偶性,利用噪声平衡块误差分散方法调整像素块的奇偶性实现水印嵌入。通过像素块的奇偶性和投票策略来实现水印的盲提取。实验结果表明,与同类算法相比,提出算法能够获得较高且灵活的水印率,并能从被攻击的嵌水印图像直接提取水印,无需将其先转化成半调图,同时能够很好地抵抗各种常见攻击以及不同型号设备的打印—扫描攻击。

A robust halftone image watermarking method was proposed.The method was developed in parity domain based on pixel block.Especially,the parity sum of a pixel block was defined by comparing the average of the pixel block with an image-dependent threshold.By altering the pixel block＇s parity based on noise-balanced block error diffusion,watermark was spread into the host image.Watermark was retrieved by employing each pixel block＇s parity and majority voting strategy,not referring to the original image.Compared with the state-of-the-art method in parity domain,the results indicate that the proposed method has high watermark rate and watermark rate flexibility.Moreover,it is capable of extracting watermark directly from the attacked watermarked image without quantizing it into a halftone image.And it can achieve high robustness against common attacks and print-and-scan attack of different types of printers and scanners.