Study On A Semi-fragile Image Watermarking Based On Genetic Algorithm

With the development of internet and the widespread use of computer, digital image can be downloaded and modified easily from internet. Therefore, how to protect the owner's copyright of digital image has become an important issue. Digital image watermarking scheme is an appropriate way to solve this problem, and millions of researchers are now involving in the research of digital image watermarking.Semi-Fragile watermark has attracted attention due to its important role in content authentication for multimedia. In order to differentiate incidental attacks and malicious attacks, semi-fragile watermark must be robust against content-protection image processing. Semi-fragile watermark resisting to JPEG compression while maintaining high detection ability to tamper has been the emphasis in the area. Our works are introduced as following:(1). In this paper, image wavelet coefficient LH2 and HL2 was blocked, and computed each of block coefficient energy, based on the relative energy relations embedded watermark. Simulation experiments prove that it will not degrade the objective and subjective quality of original images, good robustness to JPEG, and the larger amount of embedded information. What's more, it can ascertain the position of vicious attack exactly.(2). This paper proposes a new Semi-Fragile digital image watermarking scheme based on genetic algorithm (GA). After researching on several human visual systems that are used in digital image watermarking, the scheme constructs a classified model for digital image locations by considering brightness and texture. Genetic algorithm used for optimizing embedding strength and genetic is employed to optimize embedding location. Experimental results show that our scheme is better than the others.Based on the researches, our schemes are simulated on the platform of Matlab 7.0. Two systems have been accomplished, one is based on Semi-fragile image watermarking and the other is based on genetic algorithm Semi-fragile image watermarking. The first is used for an immediate situation. Although the time that is consumed by the other system is long, we will obtain better results than the first one. Experimental results show that our scheme is robust to the conventional image processing, such as JPEG compression, and fragile to malicious tampering.. Also, our scheme is better than the others.