Researches On Digital Image Watermarking Technology Based On The Wavelet Transform Domain

With the increasing convenience of the distribution of digital arts and the rapid development of the Internet, the copyright protection of digital arts is becoming more and more pressing. A watermarking system will be an effective and valuable tool to solve it. In former method, the watermark is usually the pseudo-random sequence. When detection, the result is either existing or not exist. Because business requires that watermark can represent some information, researches on meaningful watermarking are more essential than non-meaningful watermark.This paper, taking still images as example, make deep researches toward robust digital watermarks and fragile digital watermarks according to two principal applications, that is authentication and copyright protection. Respectively proposes a improving gray-level image watermarking algorithm based on data syncretism: Combining discrete wavelet transform with data syncretism is a trait of this algorithm. The process of embedding watermark is the addition of wavelet coefficients between the watermark and the carrier image of corresponding bands with the same weightiness based on the human visual system (HVS). The result of algorithm's improving not only enhances the occultation of the texture of the watermark, but also preferably protect the important component of the watermark; The second algorithm is the binary image watermark algorithm based on quantized method: The specialty of this algorithm is the application of the technology of error-correcting coding and 2-D interleaving, effectively improving robustness. The design of formula of watermark embedding primely balances the contradiction between transparence and robustness, moreover, it's a blind detection watermark since we detect the watermark without the original image; At last, a fragile watermark algorithm based on the content of the original image is proposed: Because authentication watermark needs occur corresponding change along with the change of the original image, the watermark ought to be produced based on the content of the original image. This algorithm utilizes JND threshold model of DWT domain to embed watermark values, able to primely distinguish common image processing from vicious tamper and be sensitive to vicious tamper and effectively orient the region of tamper.