Research Of Robust Digital Image Watermarking Algorithms

In the end of 20'Th century, the digital revolution included computer network and multimedia techniques brings limitless convenience for people. However, the problem about the intellectual property rights has become increasingly serious. As an effective solution to this problem, digital watermarking which embeds an imperceptible signal (watermark) into the multimedia data in order to defeat unauthorized copying and intentional tampering has attracted large numbers of attention in the information security field. Recently, there are many unresolved problems in the digital image watermarking field. The robustness is one of the problems and the watermark synchronization is very crucial to design robust image watermarking scheme. Therefore, how to develop the robust digital image watermarking schemes against de-synchronization attacks has been a key problem in the past years. In this paper, three novel image watermarking schemes are proposed to cope with the de-synchronization attacks.1, a normalization DWT (Discrete Wavelet Transform) domain based image watermarking algorithm has been presented. Based on image normalization and DWT technique, the watermark is adaptively embedded in the DWT domain in accordance with the conceal quality of HVS (Human Visual System). This is a blind watermark algorithm to confirm the copyright without the original image. Experimental results show that the proposed scheme is not only invisible, but also robust against common signals processing and global geometric distortion.2, an adaptive characteristic regions based image watermarking algorithm has been presented. The robust feature points are extracted by using Harris-Laplace detector. Based on the scale-space theory, the adaptive characteristic regions are constructed in accordance with the positions and characteristic scale of the feature points. The watermark is repeatedly embedded into all regions by modulating the magnitudes of DFT coefficients. Experimental results show that the proposed scheme is invisible and robust against common signals processing such as median filtering, sharpening, noise adding, and JPEG compression etc, and de-synchronization attacks such as rotation, scaling, translation (RST), row or column removal, cropping, and random bend attack (RBA) etc.3, a neural network based halftone image-watermarking algorithm has been presented. Through considering the features of halftone processing, the neural networks technique is applied to adjust the error diffusion kernel adaptively, which can integrate the data embedding with the halftone processing in our algorithm. Experimental results show that the proposed halftone image watermarking is invisible and robust against various signal processions such as JBIG compression, noise adding, cropping, daubing and print-scan.