Robust Screen-Shooting Document Watermarking for Multiple Fonts

The popularity of digital devices and the importance of information which lies in text documents lead to the overflowing of screen-shooting attacks for text documents nowadays. So the robust screen-shooting watermarking for text documents is in great demand. However, the existing watermarking of text documents in traditional channels which is widely researched is not available under the huge distortion from screen-shooting attacks. To tackle this problem, in this letter, watermarking based on text document structures which can persist in both print-camera and screen-shooting processes is developed. Our method has two main advantages: 1) Extensive robustness. We define partial brightness integration accompanied with stroke separation method to embed watermark information on characters. For various documents with different fonts' styles, fonts' sizes and different languages' fonts, it shows great performances. Besides, for different shooting conditions such as different shooting distances and angles, the accuracy is also guaranteed. 2) Great imperceptibility. By introducing special divisional method and adaptive intensity, high visual ability is achieved. Both of these two merits are verified by massive experiments.