| 摘要 |
The present invention provides a method and a system for embedding and extracting an image digital watermark. The method for embedding an image digital watermark includes: performing a DWT on an original carrier digital image to obtain two intermediate frequency coefficient matrixes; firstly performing a DCT on one of the two intermediate frequency coefficient matrixes, then performing the DWT, and then selecting an obtained low frequency coefficient matrix as a first low frequency coefficient matrix; performing the DWT on another intermediate frequency coefficient matrix, and then selecting an obtained low frequency coefficient matrix as a second low frequency coefficient matrix; and adjusting magnitude of a first frequency coefficient and a second frequency coefficient at various same embedment locations in the first low frequency coefficient matrix and the second low frequency coefficient matrix according to watermark values to be embedded at said embedment locations to make a magnitude relationship between two adjusted low frequency coefficients comply with a corresponding relationship between a preset embedded value and a magnitude relationship between the two low frequency coefficients. Extracting the watermark is only required to perform the inverse transform according to the method for embedding the watermark without the original carrier image during extracting the watermark.
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