Abstract:

Text visible watermarking is mainly used for determining copyright of the text digital media in order to prevent illegal usage. In order to overcome the drawback that the existing text visible watermarking algorithms have weak binaryzation attackresisting capability, the paper proposes a selfadaptive text visible watermarking algorithm based on uniform distribution of gray level, according to the characteristics of gray level and texture of text image. Firstly, the rowoutline of the cover text image is extracted, and the embedding strength of watermark is determined by the outline; Secondly, the embedding strength is used to select the black pixels of watermark. Finally, the cover text image and the watermark are mapped to the same graylevel range. The algorithm has advantages of adaptive embedding strength, random embedding position and strong binaryzation attackresisting capability. The experimental results show that the algorithm has good visibility and robustness and it can apply to any forms of text and graphics watermark.

Key words: text image;visible watermarking;binaryzation attack