Robust Watermarking for Text Images Based on Arnold Scrambling and DWT-DCT

With the popularization of Internet and the development at full speed of the multi-media technology, the copyright protection of digital works has already become the hot issue at present. The paper proposes a blind watermarking algorithm for text images' authentication and protection based on DWT-DCT. Firstly, the text image is decomposed into a low frequency, horizontal, vertical and diagonal four components though DWT transformation, then the low frequency component is made the whole DCT transform to get rid of coefficient correlation in order to obtain the visual feature vectors. Based on the studies of the document digital watermarking methods and techniques, this dissertation presents that the problems of existed documents watermarking algorithms can be solved by Arnold Scrambling and DCT technique. The experimental results show that the scheme has strong robustness against common attacks and geometric attacks.