Abstract:
A combined DWT and DCT based watermarking
technique with low frequency watermarking with weighted
correction is proposed. DWT has excellent spatial localization,
frequency spread and multi-resolution characteristics, which are
similar to the theoretical models of the human visual system
(HVS). DCT based watermarking techniques offer compression
while DWT based watermarking techniques offer scalability.
These desirable properties are used in this combined
watermarking technique. In the proposed method watermark
bits are embedded in the low frequency band of each DCT block
of selected DWT sub-band. The weighted correction is also used
to improve the imperceptibility. The extracting procedure
reverses the embedding operations without the reference of the
original image. Compared with the similar approach by DCT
based approach and DWT based approach, the experimental
results show that the proposed algorithm apparently preserves
superior image quality and robustness under various attacks
such as JPEG compression, cropping, sharping, contrast
adjustments and so on.
