一种大容量的半色调图像水印算法

在半色调图像中隐藏信息是解决印刷品的版权保护、来源认证和防止伪造等问题的有效措施。提出了一种能在半色调图像中嵌入大容量数据的隐藏算法,该算法利用误差扩散算法将待隐藏的信息作为误差信号嵌入到与该位置相邻的多个像素上，信息嵌入与半色调处理同步完成。实验表明本算法能将一幅与半色调图像同样大小的二值水印图像嵌入到半色调图像中，载有水印的图像在经受一定的噪声干扰、污损和旋转的情况下，仍能有效提取水印图像。该算法可用于普通证件的防伪。

Watermarking algorithm of large capacity halftone image

Hiding information in a halftone image is an effective method to solve copyright of presswork, source authentication, forgery prevention and so on. A hiding information scheme was proposed, in which large capacity information can be embedded in a halftone image. The hidden information was regarded as error signal first, and then Error Diffusion Algorithm was used to embed it into several pixels around a position. Moreover, information embedding and halftone processing were completed simultaneously. Experiment shows that binary watermarking image embedded may be the same as halftone image in capacity. Furthermore, under conditions of noise disturbance, dirt and rotation, watermarking image can still be extracted from the embedding watermarking image. This scheme is available for forgery prevention of general documents.