| 摘要 |
PROBLEM TO BE SOLVED: To simplify inner product calculations of a DCT coefficient which are necessary, when an electronic watermark is detected in a frequency region. SOLUTION: An apparatus 10 for detecting electronic watermark comprises an electronic watermark pattern generator 11 for generating a electronic watermark pattern W to be detected which has predetermined properties in a frequency component, the electronic watermark pattern W generated by the generator 11, and a correlation detector 12 for detecting an electronic watermark component detected value WM of a correlated value with image data Y to be detected in the frequency region. In this apparatus 10, the detector 12 executes an inner product calculation, using only the main frequency components of the DCT coefficient matrix of the pattern W, and the image data Y to be detected, based on the properties of the pattern W.
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