1. Interword Distance Changes Represented by Sine Waves for Watermarking Text Images Author: Ding Huang Supervisor: Prof. Hong Yan

2. 1. Introduction n The Problem: Because the wide spread use of the Internet facilitates content distribution, copyright can be easily infringed. n Digital Watermarking as a solution: One human being is distinguishable from others by their fingerprints or iris patterns. Similarly, a digital watermarking scheme can be used to trace the party who infringes copyright laws. n Requirements for Digital Watermarking: Perceptual transparency, unambiguity, robustness, tamper-resistance.

3. 2. Objective n Because of the binary nature of text images, digital watermarking schemes for text are very limited. n Our aim is to develop new watermarking methods for text images, including – Private (nonblind) watermarking - which requires at least the original data to recover the watermark information. – Public (blind) watermarking - which requires neither the original data nor the embedded watermark to recover the watermark information.

4. 3. Methods

6. 3.1 Private Watermarking

7. 3.2 Public Watermarking

8. 3.3 Modification of a Text Line

9. 3.4 Detection

10. 4. Results and Discussions

11. 5. Conclusions n The space pattern is an unique feature of a text and is exploited for digital watermarking. n Watermarking information spreads in 2D and is robust against interference. n Both private and public watermarking methods for text images have been developed. n Overall, our method is better than previous methods in digital watermarking for text documents (line shifting, word shifting, feature coding).

12. An Example: the original text

13. Text after private watermarking

14. Text after public watermarking