Digital watermark is an important technology for information hiding, which focuses in copyright protection. Recently, most of the researchers focus in security and robustness of digital watermark, but few researches in the capacity problem. The more applications can be reached if a large digital watermark can be embedded into the materials. This thesis proposes a watermark region of interest (ROI) concept to divide watermark into two parts and embed into frequency domain and spatial domain simultaneously. In the frequency domain, this study uses the discrete wavelet transform to embed the clipped watermark ROI into the transformed low-band. In the spatial domain, uses the least significant bit to embed the unclipped digital watermark. The proposed digital watermark technology not only enhances the capacity, but also holds the security and robustness. The main reason for embedding digital watermark into two domains, that it is very difficult for illegal detection and extraction. Experimental results show the proposed technology with large capacity, high security and robustness is adaptive to solve the image copyright protection. In the application of the large digital watermark proposed by this thesis can combine information hiding technology to embed annotations into image for searching and declaration of copyright due to our large digital watermark technology.
