Research On Algorithm And Applications Of Digital Image Watermarking Technology Based On The Wavelet Transform Domain

With the rapid development of computers and internet, copyright protection of digital media as image, video and audio becomes more and more important. Digital watermarking is a new resolution for copyright protection and media security, it is becoming a very active research area for information security. Digital watermarking is the technology which embeds copyright information including product ID, text content or image logo into multimedia for copyright protection, secret communication and discrimination of the data files. Perceptual invisibility, robustness and safeness are the digital watermarking system's central characteristics.The digital watermarking technology based on spatial domain has characteristics of computer briefness and bagger embedded capability, so it has been abroad studied in the first stage of watermarking technology. But gradually it has been replaced by watermarking technology based on frequency domain because of its disadvantage of robustness. The Wavelet Analyze can separate a spatial domain signal to some different frequency subbands by Multi-Resolution Analyze(MRA), and Human Visual System(HVS) has the characteristics of higher sensitivity to the lower frequency signal and lower sensitivity to the higher frequency signal. So the technology based on Wavelet Transform is often used to the digital watermarking field.Based on the research and the problems that exist to be considered and solved, two adaptive watermarking algorithms in wavelet domain for images are proposed. Experimentation proves that the watermark can also be extracted or detected if the digital watermarking system is attacked by adding noise, filtering, cropping, JPEG compression and so on.This thesis first discusses about the status quo and the related technologies of Digital Watermarking; then introduce the basic theory of Wavelet and Image Scrambling Algorithm as theory basis of realizing digital watermarking Algorithm. Generally, the thesis is trying to discuss on the two main aspects;(1) The thesis put forward Image-adaptive Watermarking Algorithm in DWT Domain. It's tested that it not only has the the invisible character, but also has a better robustness against the attack of image noise and filtering.(2)The thesis put forward the color Watermarking Algorithm in DWT Domain based on LAB space:first converse the RGB color space of cover image into XYZ color space, then into LAB color space, and at last instill the Scrambled watermarking into the weight of color images. The result of the experiment shows that it has a good robustness on the attack of the common JPEG lossy compression, addition of noise, median filtering, cropping.