Digital Signal Processing Reference
In-Depth Information
Figure 2.11. Wavelet transform of “Lena” by Feauveau's algorithm.
Computing the wavelet transform using the lifting scheme consists of several
stages. The idea is to first compute a trivial wavelet transform (the Lazy wavelet)
and then improve its properties using alternating lifting and dual lifting steps. The
transformation is carried out in three steps (see Fig. 2.12):
1.
Split:
This corresponds to Lazy wavelets, which split the signal into even and
odd indexed samples:
c
j
[
l
]
=
c
j
[2
l
]
c
j
[
l
]
=
c
j
[2
l
+
1]
.
(2.30)
c
j
c
j+1
+
c
j
−
P
U
w
j+1
c
j
+
Figure 2.12. The lifting scheme, forward direction.
