The Study Of Image Watermark Base On Discrete Wavelet Transformation

With the rapid development of computer and information encryption technology, information hiding, the hot technology in the information security field, has been given more attention by academic and industrial society. The development of information operation leads a great challenge to the security of military communication, and the application of information hiding technology to military concealment communication will greatly improve the security of information transmission. In this paper, the technique of hiding information in image was studied. The main achievements can be summarized as follows:This thesis puts extra emphasis on how to insert and abstract the digital image watermark technology. After researching and analyzing the basic knowledge of digital watermarking technology and discrete wavelet transform, an image watermarking algorithm basing on embedding information in the middle-frequency and low-frequency coefficients of wavelet transform was proposed This algorithm to make full use of wavelet transform the characteristics of the original image and the watermark image decomposition tower, the method has the advantage of HVS, simple and effective algorithm. Experiments have proved that the algorithm can solve the watermark invisible robustness and the contradiction between, on the common watermark attacks have robust. Under the simulation platform of Matlab, and tested the robustness of the algorithm by noisy attack, JPEG compression, cropping attack, and other offensive experiments. Experimental results showed that the algorithm proposed in this paper, by which information is embedded in the coefficients of wavelet transform, performed robust after the common signal processing operations, especially in the experiments of anti-JPEG compression and anti-filtering attack, the algorithm performed excellent.Through the digital image decomposition and reconstruction in wavelet domain, as well as the characteristics of the watermark image analysis,a new image watermarking algorithm of hybrid transform domain is proposed. The wavelet coefficient of the original image is got through wavelet transform, and the low frequency coefficient is seen as a sub-image. Then the binary watermark image is permuted, the watermark is embedded into the coefficient which got from the DCT of the sub-image. Through various experiments of attacking to the watermark on images, the results shows that the embedded watermark is not easy to detect after using this algorithm. The extracted watermark has perfect effect, for JPEG compression, cutting, noise and Low-pass filtering and other attacks, it reveals a stronger robustness.The application of information hiding in the military communication was discussed. A novel concealment communication system based on image information hiding was proposed. The algorithm presented in this thesis belongs to the embedding-extracting watermark algorithm. It doesn't need the original watermark and vector information in the process of extracting. Moreover, the algorithm uses a kind of secret Keys established by certain rules, this enables it to meet the basic conditions for the military secure communication.