Image Processing Reference
In-Depth Information
N
N
B
0000
N×N -
point
DFT
Zero
padding
f
i
(
n, m
)
0000
0000
F
i
(
k, l
)
f
i
(
n,m
)
0000
B
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
N
N×N
-
point
IDFT
g
i
(
n, m
)
N
N
L
0000
Zero
padding
0000
N×N -
point
DFT
h
(
n
,
m
)
0000
0000
h
(
n,m
)
H
(
k, l
)
L
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
FIGURE 2.23
Filtering an image block using DFT.
B
N
…
…
…
…
FIGURE 2.24
Overlap and add technique.
We then convolve each block with h(n, m) using the DFT approach as outlined
in Section 2.5.1 and shown in Figure 2.23. That is, for i ¼
1, 2,
...
, N
B
we
compute,
g
i
(n, m)
¼ f
i
(n, m)
*
h(n, m)
(2
:
70)
Note that the 2-D DFT computation is performed using row
column decompos-
-
ition and a 1-D FFT algorithm.
The output image is formed by overlapping and adding these N
B
blocks as
illustrated in Figure 2.24.
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