Information Technology Reference
In-Depth Information
quality measure (IQM) steganalysis attack [4, 5, 8, 9]. Different color
spaces are incorporated in the proposed scheme (i.e., RGB, YCbCr, and
HSV) to ensure that the visual artifacts appeared in the stego-image are
imperceptible, and the differences between the cover and the stego-image
are indistinguishable by the human visual system (HVS) [10, 11].
4.2
MATERIALS AND METHODS
4.2.1 DISCRETE WAVELET TRANSFORM AND THE SCALING
FACTOR FOR ENERGY ADJUSTMENT
Wavelets provide a mathematical flexible tool for practical problems in
science and engineering. One of the principal properties of the wavelets is
that they allow modeling better processes that depend strongly on the time
and whose behavior does not have for what to be smoothing. DWT is par-
ticularly effective for extracting information from nonperiodical signals of
finite life and it is closely linked to the analysis of multiresolution (MRA),
that is, see the signals at different frequencies [12], which allows to have a
broader knowledge of the signal and facilitates the rapid calculation when
the wavelet family is orthogonal [13-16].
It can be obtained wavelets
⎧
⎫
⎛
j
⎞
1
t
−
2
n
()
such that the
⎜
⎝
⎟
⎠
ψ
t
=
ψ
j
,
n
j
2
2
j
⎩
⎭
2
j
,
n
∈
Z
L
2
.
The orthogonal wavelets transport information about the changes of the
signal to the resolution 2
−j
. Then, the MRA appears: an image is mod-
eled with orthogonal projections on vector space of different resolution,
()
family moved for
j
and dilated for
n,
it is a orthonormal basis of
()
IR
PfV L I
Ì
. The quantity of information in every projection depends
on the size of
Vj
. For search orthogonal wavelets, it will be necessary to
work with approaches of MRA [13, 14, 15, 17, 18]. For a function
2
,
V
j
j
()
2
f
Î
L R
∞
=−∞
<
∑
can be interpreted
as the difference between two approaches of
f
for the resolutions 2
−1+j
and
2
−j
. The MRA approaches calculate the approach of signals to different
resolutions with orthogonal projections in spaces
{}
, the partial sum of the coeffi cients wavelet
f
,
ψ
jn
,
n
V
Î
. The approach
of a function of a resolution 2
−j
is defi ned as an orthogonal projection in a
space
()
j
jZ
j
VLIR
. The space
Vj
regroups all the possible approaches to the
resolution 2
−j
. The orthogonal projection of
f
is the function
2
f
Î
that
j
j
minimizes
f
−
f
. The orthonormal wavelets carry the necessary details
j
Search WWH ::
Custom Search