| Similar to the watermarking of cash, digital watermarking is defined to embed special information, for examples, owners, publishers and buyers of digital copyright works, or data and serial numbers and so on, in digital image, audio, video and texts by embedding techniques so as to identify the copyright and be used as prove in law as well as to protect intellectual property rights and digital multimedia by testing and analyzing digital watermarking. Digital watermarking is the implementation for traditional cryptography.The main point of this text is to study DCT-based (Discrete Cosine Transform) image digital watermarking and focus on how to choose proper locations in DCT parameters for embedding watermarking so as to get better performance than other algorithms in general anti-shear attack while meeting invisibility.Generally speaking, the usual means to do shearing are including shearing one edge, a couple of edges which are close to each other, and shearing a part of image inside. According to common rules, the data of an object in a image should be located close to each other and the object abides by the rule of gravity. Now since that will be the base of algorithm, we could get the correlation-ship between the left-up part and the right-down part into the solution to goal of anti-shearing, for just one of them will be involved in the part being sheared. Then we could increase the probability of extracting the right watermarking so as to avoid the likeliness decreasing to zero. |
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