The Research On Digital Image Watermark Based On Wavelet

With the rapid development of computer network and communications, it is easier to generate, copy, transmit the digital information than ever before. In this situation, the new subject has been presented to prevent the transmission of digital data without authorization. That is digital watermarking, which embeds an imperceptible signal (the watermark) into multimedia data such as image, video, and audio, and it has attracted considerable attention in the past few years.In the thesis, we first introduce the history and origin of information hiding and digital watermark techniques, and then discuss digital watermark techniques including the conception of digital watermark, the applications of digital watermark, the classification of watermark technology and basic requirement, the composing of watermark system and general theory, and the classification of watermark attacks. At the last, we proposed two new image watermarking algorithm based on wavelet.The first scheme is robust watermarking algorithm for image copyright protection. We propose a new watermarking scheme by embedding a digital image signature/watermark in the wavelet domain and spatial domain. The watermark is disparted into two parts. One part is inserted in the low frequency sub-bands of wavelet domain. The other part is inserted in spatial domain directly. There are two steps in the watermark extraction .We can get the original watermark image from the two steps. This method not only has the robustness but also increase the capacity of hiding data.The second scheme is a semi-fragile watermarking algorithm for image authentication. We propose a novel, yet simple, image-adaptive watermarking scheme for image authentication by applying a simple quantization-index-modulation process on wavelet packet domain singular value decomposition. The proposed scheme is based on bit embedding on the singular value of the blocks within wavelet packet subband of the original image. The scheme is robust against JPEG compression but extremely sensitive to malicious manipulation such as filtering and random noising. Watermark detection is efficient and blind in the sense only the quantization parameters but not the original image are required.