Research And Implement Of Digital Watermarking Technique Based On Image Content

With the development of Internet and multimedia processing technique, media can be conveniently expressed, storaged, obtained and distributed in the form of digital. However, digital media can be copied and transmitted with the low cost and high speed, coping and processing digital media nonlicetly is easy. So the protection of copyright becomes a serious problem. Digital watermarking technique is an important method of protecting copyright. The watermarking technique based on digital multimedia content is hot research in the range of digital watermarking, which can solve the shortage of resisting geometry attack effectively. Feature extraction is the key of the content based watermarking algorithm. Feature can be extracted either in the space domain or in the frequence domain. This paper researches the watermarking technique based on image content. Achievements sum up as follows:1. In image space domain, the shortcoming of the existed image watermarking algorithms based on Harris feature point extraction is analysied and a new watermarking algorithm based on Harris feature point extraction is proposed. The new algorithm first improves the Harris feature point extraction algorithm based on image texture, then forms the embedding area with the center of each extracted point and adjusts the embedding strength based on the gray masking and the texture masking of the local embedding area. The experimental results show that the proposed algorithm can resist cropping attack and noise attack very well.2. In image frequence domain, considering the structure and energy of the Zerotree Wavelet, a new watermarking algorithm is proposed based on image block feature extraction.The proposed algorithm first extracts those image blocks that all wavelet blocks they responded in all resolutions and subbands have bigger energy as feature blocks, then imbeds the same watermark sequence in all the extracted image feature blocks using quantization embedding idea. The experiments show that the proposed watermarking algorithm is robust in noise, image filtering, image cropping and partial image rotation.3. An image content based watermarking prototypical system is designed based on the proposed algorithms.