Image Digital Watermarking Algorithm Research

In recent years, with the Internet and digital multimedia technology, the production, replication and transmission of digital multimedia products become convenient and fast. At the same time, their copyright protection and authenticity and integrity of content testing has become an urgent problem to be solved. Digital watermarking technology, as an effective means of intellectual property protection and digital multimedia content authentication has become a new field of study of information security.First, this paper describes the background of digital watermarking, the status of domestic and foreign research and the basic theory of digital watermarking. For digital watermarks have a contradiction between existence and robustness in image copyright protection, we proposed a zero-watermarking algorithm based on DCT transform and chaotic system. Based on the DCT-block, we used the chaotic system to extract the DC component, which had been normalized to produce zero-watermark. Experimental results showed that the algorithm can solve the contradiction between the perception and robustness. It had a good stability to conventional image processing, such as JPEG compression, adding noise, median filtering, cropping and rotating the image.For most image authentication algorithms can not distinguish between watermark been tampered with, the image content been tampered with, or both been tampered with and tampered localization can not accurate and quality of recovery needed to be improved, we proposed a self-embedding watermarking algorithm based on singular value decomposition. Through singular value decomposition, the largest singular value of each block had been quantized to generate recovery watermark. And each singular value norm had been binary coded to generate authentication watermark. Then embed recovery watermark which had been scrambling encrypted into the sub-low areas and embed authentication watermark which had been encrypted into the lowest areas. The results show that dual watermark can not only distinguish between the content and the watermark to be altered or tampered with, but the content can be tampered region 2×2 image blocks of precise location and restorate altered areas approximately. The restoration quality is good.