关键词: PDF文档, 文本水印, 字符颜色编码, 隐蔽性, 鲁棒性

Abstract:

For the current significant contrast between the active usage rate of PDF documents and the slow development of their digital watermarking technology,a text watermarking algorithm based on character color of PDF is proposed.The algorithm embeds the pre-processed watermark into PDF carrier document by modifying the operand of character color operator of PDF.The security and robustness are enhanced by using channel coding and cycle encryption in pre-processing of watermark insertion as well as majority voting in post-processing of watermark extraction.Experiments show that the algorithm has good transparency,strong robustness,high capacity and good compatibility with PDF.

Key words:  PDF document;text watermarking;character color coding;transparency;robustness