Patent ID: 8615103

Claim:
A method for embedding an image digital watermark, which comprises: performing a discrete wavelet transform (DWT) on an original carrier digital image to obtain two intermediate frequency coefficient matrixes; firstly performing a discrete cosine transform (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.