On Watermarking Embedding And Extracting Algorithms For Digital Document Images

Digital document watermarking technology can be used to solve effectively the copyright protection problem of digital document media. Recent years, the study is dispersive relatively, and is short of system theory, moreover is out of breakthrough.This thesis mainly studies watermarking embedding and extracting algorithms for digital document images according to their characteristics. First the basic conception, the current research states and the application conditions of digital document watermarking are introduced, then the existing algorithms and their features are analyzed, the classification and the evaluation for digital document images are given, finally the emphases are focused on the space and the transform domain watermarking algorithms for digital documents. In space domain, line shift and word shift coding are used to embedding a watermark in a digital document according to their structure characteristics, the embedding and extracting algorithms are implemented. The experimental results show that this algorithm is effectively and has strong robustness. In transform domain, the discrete cosine transform (DCT), discrete wavelet transform (DWT) , DCT-DWT and blocked DCT-DWT algorithms are studied, the embedding and extracting process are realized in MATLAB language. The experimental results show that these algorithms can embed and extract watermark information effectively.