Digital Watermarking Based On Spread Transform Dither Modulation

With the rapid development of the information technique and computer network, the storage, copy and distribution of the digital multimedia is becoming more and more convenient, and people's life and work is becoming digitalized and network-connected. Since then, information security, pirate and copyright problem have come to be society problem. Against this background, digital watermarking technology, which can hide digital information in multimedia products, is receiving careful attention in the scientific researches, industries, as well as the governmentDue to its sound application flexibility, blind watermarking schemes (i.e., algorithms in which the watermark can be extracted without resorting to the original unmarked signal), have received widespread attentions. Quantization index modulation (QIM) is the representative method among those schemes. It is well known that spread transform dither modulation (STDM), as an extension of QIM, has good performance in robustness to common signal processing operation. In this paper, two novel watermarking schemes are presented, one of which can significantly improve the fidelity of the watermarked image, and the other one can embed any quantity of watermarks into the same area and the same transform domain of one image.The works in this thesis are as follows:1. We apply a novel way to incorporate the perceptual model with STDM framework based on the Step-Projection idea. That is projecting the perceptual slacks of the host vector along the direction of the random projection vector to adaptively select the quantization step. Experimental results indicate that the proposed step projection based approach can incorporate the perceptual model with STDM framework in a better way, thereby providing a significant improvement in image fidelity. Compared with former proposed modified schemes of STDM, our best performed scheme, STDM-SP-wm, provides powerful resistance against the common attacks, especially in robustness against Gauss Noise, Salt\&Pepper Noise and JPEG compression. We further proposed a video watermarking algorithm based on step projection based STDM. Experimental results indicate that our proposed scheme has good robustness against video compression, and can provide watermark certification even under the extreme low compression rate. 2. A novel multiple watermarking algorithm was proposed which initially extend the STDM, a single watermarking algorithm, to the field of multiple watermarking application. It can embed any quantity of watermarks into the same area and the same transform domain of one image; meanwhile, the embedded watermarks can be extracted independently and blindly in the detector without any interference. Moreover, to improve the fidelity of the watermarked image, the properties of the dither modulation quantizer and the proposed multiple watermarks embedding strategy were investigated, and one practical optimization method was proposed. Experimental results indicate that the optimization procedure can significantly improve the quality of the watermarked image, meanwhile, the more watermarks embedded the more quality improvements can be gained. Finally, to enhance the application flexibility, an extension of our algorithm was proposed, which can sequentially embed any numbers of multiple watermarks into the image during each stage of its circulation, thereby realizing image history management. In general, compared with the pioneering multiple watermarking algorithms, the proposed scheme owns more flexibility in practical application and is more robust against distortion due to basic operations such as random noise, JPEG compression and valumetric scaling.