Multi-scale Morphological Gradient-based Adaptive Digital Watermarking Algorithm

With the multimedia and network technology of development and application,it has become an important problem to protect the multimedia content,which is concern and needs to resolve.As a very important type of multimedia information,copyright protection and content authentication for digital image is regarded widely.So,digital watermarking technology becomes the powerful measure to protect the safety and effectiveness of information.There are a lot of digital watermarking algorithms.In recent years,digital watermarking technology becomes a hot area of the digital watermarking research.Based on this study of digital image watermarking,this thesis mainly has done a systematic study of entire digital watermarking,and the main work is as follows:The thesis introduces the basic model,the characteristics,classification and application of digital watermarking technology,and focus on analysis of the existing typical watermarking algorithm of the technology strategy and its advantages and disadvantages.Based on the depth analysis and study of existing digital watermarking algorithm, the thesis focus on the digital watermarking in DWT,especially is committed to adaptive digital watermarking algorithm design.Through improving flaws of existing adaptive algorithms,an adaptive watermarking algorithm in the wavelet domain based on morphological gradient is proposed in this paper.Using morphological gradient,the distribution and the strength of the sub-block texture after the wavelet package decomposition are analyzed,and the texture is sorted. According to the texture feature of the sub-block,the sub-block threshold is determined adaptively and the position which is bigger than its threshold is selected as the important coefficient position where the watermarking is embedded.Then,the strength of the position is modulated adaptively through Noise Visibility Function(NVF),which is the best strength to ensure good visual effect of masking to achieve the best effect between robust and invisibility.A large amount of experiments show that the proposed algorithm is effective and robust to common image processing operations.