Digital Watermark Research Based On Wavelet Domain

With the development of computer networks, especially the Internet technology, multimedia information can be exchanged wildly and easily by the Internet. Then how to implement effective copyright protection and ensure the security of information in the network environment has greatly aroused attention of international academia, the business community and the relevant government departments. Digital watermarking is a very effective technique for the protection of intellectual property rights and digital multimedia security. The copyright information─digital watermark is embedded into digital products to verify their ownerships. The embedded watermark information is usually invisible or imperceptible. However, a detector can be used to extract it or determine its existence. Recently, this technique has become a hot spot in research of multimedia information security.Digital watermarking is still in his infancy, and many problems remain yet to be solved. This paper addresses research of image digital watermarking algorithm.The main tasks are summarized as follows:1. As the processing of watermark-scrambling is taken into account, scramble theories such as Arnold transformation is introduced and the simulation is also implemented by the computer.2. A digital watermark algorithm is designed based on the characteristics of discrete wavelet transform. Firstly this algorithm decomposes the original host image into three levels. Then the digital watermarking is randomly scrambled by Arnold transformation and is inserted into the low frequency coefficients of the three-level wavelet domain. Watermarked image is obtained by inverse discrete wavelet transformation. Then the image is decomposed by three-level discrete wavelet transformation, and the watermarking is extracted through a certain way. Finally the primitive watermarking is obtained by anti-Arnold transformation. The watermark extraction process does not require the original image, and it is truly a kind of blind watermark.3. Then the embedding location of the watermark under the premise of the abovestrategy is chosen according to block energy analysis strategies. We chose the block which has the largest block-energy on the same position of the selected wavelet domains, and then select the largest absolute pixel point to embed the watermark. The experimental results demonstrate that the embedded watermark is not only invisible, but also robust against the attacks of the noise addition, filtering and so on.4. A new kind of dual watermarking algorithm based on wavelet transform and suitable for color images was proposed. The given color image is transformed from RGB color space to YUV color space first, and then we choose Y, U and V component separately to embed the watermarks and the embedding position is still selected according to block energy analysis strategies. The experimental results show that: the watermark embedded in Y-component has better invisibility and robustness than that in the U and V components separately. Finally, we embed the dual-watermark in Y, U and V components simultaneously, and experimental results demonstrate that the embedded watermark is of even better robustness.