Research On Several Digital Image Watermarking Techniques And Their Applications

With the rapid development of the digital multimedia distribution over the Internet, digital watermarking, a novel technique for copyright protection, credibility and integrity authentication of digital media, has attracted more and more attention. The research on digital watermarking is getting more and more in-depth and broad. In this dissertation, the robust watermarking for image copyright protection and the semi-fragile watermarking for image authentication are studied in detail. The main contribution includes:1. An artificial neural network (ANN) based robust zero-watermark scheme for image copyright protection is proposed. On the one hand, the strong learning and adaptive abilities of the ANN can be exploited to effectively improve the watermark performance. On the other hand, by extracting the features from an image instead of embedding watermark into it, zero-watermark technique provides a good ability for image copyright protect, while maintaining the visual quality of the image. The combination of the ANN and the zero-watermark techniques guarantees the watermark robustness as well as imperceptibility. A simple and effective zero-watermark algorithm is realized by using multilayer feedforward BP network. The proposed scheme can be used for automatic piracy detection. Cooperated with copyright authentication center, it can also be used for copyright validation.2. An ANN-based semi-fragile zero-watermark scheme for image credibility and integrity authentication is proposed. The scheme extracts image features via the ANN instead of embedding information into the image, resulting in not affecting the visual quality of the image. The extracted image features can be used for image authentication. The idea is somewhat similar to the digital signature technique in the cryptography. Different from the digital signature, the scheme achieves tampering detection as well as tampering position localization, in addition to the image credibility authentication.3. The binary phase-only filter (BPOF) based digital image watermarking is a semi-fragile watermarking technique used for the image credibility authentication. The technique constructs BPOF based watermark from the image discrete Fourier transformation and embeds the watermark into the bit plane(s) of the corresponding magnitude spectrum. The use of the inherent characteristic of an image, i.e., BPOF, as the watermark makes it unnecessary to transmit extra data and achieves image...