Digital Signal Processing Reference
In-Depth Information
a. Given corners extracted from the two images are
and
L XY i M
=
{(
,
),
=
1, 2,
,
}
R
i
i
, where
M N
are the number of corners respectively,
according to the value of cornerness measure
L
=
{(
x
,
y
),
j N
=
1, 2,
,
}
S
j
j
Wxy
,
sort the corners and get sorted
(, )
corners, represented by
'
and
'
L XY i M
=
{(
,
),
=
1, 2,
,
}
L
=
{(
x
,
y
),
j N
=
1, 2,
.
,
}
R
i
i
S
j
j
LL
,
select one corner at a time, guaranteeing the
Euclidean distance
between the second selected corner and the first selected corner less
than a preset thresh. Repeat the process until the desired number is achieved or no more
corners remain in
b. Starting from the first of
' '
,
RS
LL
.
The final extracted corners are
' '
,
RS
and
PXYi m
=
{(
,
),
=
1, 2,
,
}
i
i
Qx
=
.
The flowchart of the improved technique based on Harris is shown as fig.2.
{(
,
y
),
j n
=
1, 2,
, in this paper,
, }
mn
,
≤
0
j
j
Reference
image
Histogram
equalization
Get pixels whose gradient amplitude
is larger than an experiential threshold
Extract corners by
Harris operator
Histogram
Sensed
image
Histogram
equalization
Get pixels whose gradient amplitude
is larger than an experiential threshold
Extract corners by
Harris operator
Histogram matching
Fig. 2.
Flowchart of the improved technique based on Harris
3
Virtual Triangles Matching
3.1
Some Definitions
Definition 1: Select randomly three points from
PXYi m
=
{(
,
),
=
1, 2,
or
,
}
i
i
,
then connect them orderly to compose triangle. We call the
triangle as virtual triangle because it is not exist in the images actually.
Definition 2: We call the random two virtual triangles in reference and sensed images
as a virtual triangles pair.
Qx
=
{(
,
y
),
j n
=
1, 2,
, }
j
j
Definition 3: If three corresponding vertexes of a virtual triangles pair are corres-
ponding corners, we call them as a matching virtual triangles pair.
3.2
Virtual Triangles Matching
If the relation of two images is similarity transformation, a matching virtual triangles
pair in them are similar. Virtual triangles matching are based on the principle.
Given random three points in
are
ppp
,
random three
PXYi m
=
{(
,
),
=
1, 2,
,
}
,
,
i
i
12 3
points in
are
compose a
Qx
=
{(
,
y
),
j n
=
1, 2,
, }
qqq
.
,
,
Δ
ppp
and
Δ
qqq
j
j
12 3
123
123
virtual triangles pair shown as fig.3.
