Based On The Characteristics Of Anti-cut Digital Watermarking Technology Research

In recent years, the spread of the Internet and the advance in digital techniques for transmitting and storing information have made it possible to copy and edit images, audio, video and other types of multimedia data. Multimedia data by digital format can be duplicated without loss of quality and changed easily at low cost. These situations cause the illicit actions such as interception, duplication, misuse and unauthorized modification of information. One approach to address the problem is watermarking technique. The concept of digital watermarking is associated with the data-hiding technique. Digital watermarking has been proposed as a way to identify the source, creator, owner, distributor, or authorized consumer of multimedia data.In this thesis, the current watermark developing status, basic characters and problems of digital watermark technology are analyzed, and the general frame of digital watermark processing system is discussed and two watermarking schemes are proposed.In the first scheme, an HVS-based algorithm is proposed, which embeds a binary image in DCT domain by quantifying the coefficient of DCT's middle coefficients. The main idea is to adjust the embedded-intensity of coefficients of the DCT's domain by calculating values of texture sensitivity and frequency sensitivity and intensity sensitivity. The proposed technique can actually resist several kinds of image processing such as image cropping, blurring, noise, sharpening and JPEG lossy compression. Simulation results prove the effectiveness of the algorithm.In the second scheme, a feature-based algorithm is proposed, which embeds a binary image as watermark in DCT domain by taking into account the feature of gradient and intensity of each block. Especially, marker bits are embedded to locate the original block of cropped or row or column removed image. The proposed technique can actually resist several kinds of image processing such as image cropping, shifting, blurring, noise, sharpening and JPEG lossy compression etc. The algorithm doesn't need the original image for watermark extraction and the simulation results prove that the algorithm is effective.