Research And Implementation Of Image Digital Watermarking Technology

As an important branch of information hidden, digital watermarking is a new field in security of information and play a magnificent role in copyright protection of digital work.This thesis focuses on images. Firstly research backgrounds, basic characteristics, classifications and applications of digital watermarking are introduced. The paper formulates the basic principles and representative algorithms, and the attack of the image digital watermarking is discussed in detail. Then, based on the existing watermarking algorithm, with the chaotic theory and discrete cosine transform, design and implement an algorithm"An image watermarking algorithm based on chaotic scrambling", and a new algorithm"A zero-watermarking algorithm based on DCT"is proposed. Finally, the good performance of the two algorithms is verified by some common image processing and attack experiments.1. An image watermarking algorithm based on chaotic scrambling. This algorithm uses the Logistic mapping sequences to scramble and encrypt the binary image watermark. Then DCT is performed on the original image, and then the coefficients of intermediate frequency are used as the watermarking imbedding domain. The experimental results show that the algorithm is invisible and robust against some commonly image processing such as JPEG compression,cropping attacks and so on.2. A zero-watermarking algorithm based on DCT. Zero-watermarking utilizes the feature of the original images to construct a watermark, but does not modify the data. This algorithm takes the advantages of both DCT and the Logistic mapping sequences fully. It can solve the conflict between robustness and invisibility effectively during embedding, and it can also improve the robustness and security. The experimental results prove that the algorithm could make image distortion–free and be robust, simple, ease to use.As the two algorithms are sensitive to rotation, we bring the secondary-detecting into watermarking detection. The geometric moments of original image are exploited to estimate the rotation. So that the corrupted watermarked image can be corrected and the watermark can be detected correctly. The experimental results prove that the method can improve the robustness to rotation greatly.