  In recent years, reversible data hiding has attracted much more attention
than before. Reversibility signifies that the original media can be recovered
without any loss from the marked media after extracting the embedded message.
This paper presents a new method that adopts two-level wavelet transform and
exploits the feature of large wavelet coefficient variance to achieve the goal
of high capacity with imperceptibility. Our method differs from those of
previous ones in which the wavelet coefficients histogram not gray-level
histogram is manipulated. Besides, clever shifting rules are introduced into
histogram to avoid the decimal problem in pixel values after recovery to
achieve reversibility. With small alteration of the wavelet coefficients in the
embedding process, and therefore low visual distortion is obtained in the
marked image. In addition, an important feature of our design is that the use
of threshold is much different from previous studies. The results indicate that
our design is superior to many other state-of-the-art reversible data hiding
schemes.
