| 摘要 |
<p>An electronic watermarking method which makes it difficult to erase other information such as signature data combined with image data and which does not require the original image in extracting the information. The image signal is subjected to wavelet transform to extract a multiple resolution approximated area (MRA), which is spread to a wide-band frequency spectrum in a pseudonoise sequence (PN sequence), and signature data is incorporated into a specific part of the spread frequency spectrum according to predetermined rules. Then, the combined signals are subjected to spectrum-despreading according to the PN sequence and to wavelet inverse transform so as to generate an image signal combined with the signature data. By this method, because the signature data is combined for an MRA, It is resistant to signal processings such as filtering. Further, the use of the spread spectrum provides a high level of secrecy. Moreover, the feature of the wavelet transform can be utilized to synthesize signature data in multiple layers. <IMAGE></p> |
