Image Processing Reference
In-Depth Information
Example 2.13
Find the HT of the 4
4 image f (n, m) given as
2
4
3
5
15 15 16 14
16 17 15 13
14 11 12 15
13 12 15 13
f (n, m)
¼
S
OLUTION
F(k, l)
¼ Af (n, m)A
2
4
3
5
2
4
3
5
2
4
3
5
1111
1
15 15 16 14
16 17 15 13
14 11 12 15
13 12 15 13
1111
1
1
2
11
1
1
2
11
1
¼
11
1
1
11
1
1
1
1
11
1
1
11
2
4
3
5
56
:
51
:
500
0
:
5
0
:
5
12
F(k, l)
¼
4
0
2
:
5
2
:
5
0
1
1
:
5
1
:
5
The HT is a real and fast transform. Since the basis vectors contain only
1 values,
no multiplications are needed in the computation of the HT.
2.6 IMAGE FILTERING
Filtering images has applications in image smoothing (noise removal), image sharp-
ening, edge enhancement, and image deblurring. Filters used in image processing are
generally FIR
filters of relatively small size. An FIR
filter is also referred to as a
mask, a kernel, or a window [14]. The
filter components are referred to as
filter taps,
weights, or elements. Some examples of popular small size FIR
filters used in image
processing are
a. Low-pass
filters (LPF)
2
4
3
5
2
4
3
5
111
121
1
9
1
16
h
(
n, m
) ¼
h
(
n, m
) ¼
111
,
242
,
111
121
2
4
3
5
111
1
10
h
(
n, m
) ¼
121
(
2
:
82
)
111
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