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submodule
opencv
Commits
ea971df8
Commit
ea971df8
authored
Aug 12, 2011
by
Ana Huaman
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Added SURF_Homography sample codee
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d80a41a5
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SURF_Homography.cpp
samples/cpp/tutorial_code/features2D/SURF_Homography.cpp
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samples/cpp/tutorial_code/features2D/SURF_Homography.cpp
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ea971df8
/**
* @file SURF_Homography
* @brief SURF detector + descriptor + FLANN Matcher + FindHomography
* @author A. Huaman
*/
#include <stdio.h>
#include <iostream>
#include "opencv2/core/core.hpp"
#include "opencv2/features2d/features2d.hpp"
#include "opencv2/highgui/highgui.hpp"
#include "opencv2/calib3d/calib3d.hpp"
using
namespace
cv
;
void
readme
();
/**
* @function main
* @brief Main function
*/
int
main
(
int
argc
,
char
**
argv
)
{
if
(
argc
!=
3
)
{
readme
();
return
-
1
;
}
Mat
img_1
=
imread
(
argv
[
1
],
CV_LOAD_IMAGE_GRAYSCALE
);
Mat
img_2
=
imread
(
argv
[
2
],
CV_LOAD_IMAGE_GRAYSCALE
);
if
(
!
img_1
.
data
||
!
img_2
.
data
)
{
std
::
cout
<<
" --(!) Error reading images "
<<
std
::
endl
;
return
-
1
;
}
//-- Step 1: Detect the keypoints using SURF Detector
int
minHessian
=
400
;
SurfFeatureDetector
detector
(
minHessian
);
std
::
vector
<
KeyPoint
>
keypoints_1
,
keypoints_2
;
detector
.
detect
(
img_1
,
keypoints_1
);
detector
.
detect
(
img_2
,
keypoints_2
);
//-- Step 2: Calculate descriptors (feature vectors)
SurfDescriptorExtractor
extractor
;
Mat
descriptors_1
,
descriptors_2
;
extractor
.
compute
(
img_1
,
keypoints_1
,
descriptors_1
);
extractor
.
compute
(
img_2
,
keypoints_2
,
descriptors_2
);
//-- Step 3: Matching descriptor vectors using FLANN matcher
FlannBasedMatcher
matcher
;
std
::
vector
<
DMatch
>
matches
;
matcher
.
match
(
descriptors_1
,
descriptors_2
,
matches
);
double
max_dist
=
0
;
double
min_dist
=
100
;
//-- Quick calculation of max and min distances between keypoints
for
(
int
i
=
0
;
i
<
descriptors_1
.
rows
;
i
++
)
{
double
dist
=
matches
[
i
].
distance
;
if
(
dist
<
min_dist
)
min_dist
=
dist
;
if
(
dist
>
max_dist
)
max_dist
=
dist
;
}
printf
(
"-- Max dist : %f
\n
"
,
max_dist
);
printf
(
"-- Min dist : %f
\n
"
,
min_dist
);
//-- Draw only "good" matches (i.e. whose distance is less than 3*min_dist )
std
::
vector
<
DMatch
>
good_matches
;
for
(
int
i
=
0
;
i
<
descriptors_1
.
rows
;
i
++
)
{
if
(
matches
[
i
].
distance
<
3
*
min_dist
)
{
good_matches
.
push_back
(
matches
[
i
]);
}
}
Mat
img_matches
;
drawMatches
(
img_1
,
keypoints_1
,
img_2
,
keypoints_2
,
good_matches
,
img_matches
,
Scalar
::
all
(
-
1
),
Scalar
::
all
(
-
1
),
vector
<
char
>
(),
DrawMatchesFlags
::
NOT_DRAW_SINGLE_POINTS
);
//-- Localize the object from img_1 in img_2
std
::
vector
<
Point2f
>
obj
;
std
::
vector
<
Point2f
>
scene
;
for
(
int
i
=
0
;
i
<
good_matches
.
size
();
i
++
)
{
//-- Get the keypoints from the good matches
obj
.
push_back
(
keypoints_1
[
good_matches
[
i
].
queryIdx
].
pt
);
scene
.
push_back
(
keypoints_2
[
good_matches
[
i
].
trainIdx
].
pt
);
}
Mat
H
=
findHomography
(
obj
,
scene
,
CV_RANSAC
);
//-- Get the corners from the image_1 ( the object to be "detected" )
Point2f
obj_corners
[
4
]
=
{
cvPoint
(
0
,
0
),
cvPoint
(
img_1
.
cols
,
0
),
cvPoint
(
img_1
.
cols
,
img_1
.
rows
),
cvPoint
(
0
,
img_1
.
rows
)
};
Point
scene_corners
[
4
];
//-- Map these corners in the scene ( image_2)
for
(
int
i
=
0
;
i
<
4
;
i
++
)
{
double
x
=
obj_corners
[
i
].
x
;
double
y
=
obj_corners
[
i
].
y
;
double
Z
=
1.
/
(
H
.
at
<
double
>
(
2
,
0
)
*
x
+
H
.
at
<
double
>
(
2
,
1
)
*
y
+
H
.
at
<
double
>
(
2
,
2
)
);
double
X
=
(
H
.
at
<
double
>
(
0
,
0
)
*
x
+
H
.
at
<
double
>
(
0
,
1
)
*
y
+
H
.
at
<
double
>
(
0
,
2
)
)
*
Z
;
double
Y
=
(
H
.
at
<
double
>
(
1
,
0
)
*
x
+
H
.
at
<
double
>
(
1
,
1
)
*
y
+
H
.
at
<
double
>
(
1
,
2
)
)
*
Z
;
scene_corners
[
i
]
=
cvPoint
(
cvRound
(
X
)
+
img_1
.
cols
,
cvRound
(
Y
)
);
}
//-- Draw lines between the corners (the mapped object in the scene - image_2 )
line
(
img_matches
,
scene_corners
[
0
],
scene_corners
[
1
],
Scalar
(
0
,
255
,
0
),
2
);
line
(
img_matches
,
scene_corners
[
1
],
scene_corners
[
2
],
Scalar
(
0
,
255
,
0
),
2
);
line
(
img_matches
,
scene_corners
[
2
],
scene_corners
[
3
],
Scalar
(
0
,
255
,
0
),
2
);
line
(
img_matches
,
scene_corners
[
3
],
scene_corners
[
0
],
Scalar
(
0
,
255
,
0
),
2
);
//-- Show detected matches
imshow
(
"Good Matches & Object detection"
,
img_matches
);
waitKey
(
0
);
return
0
;
}
/**
* @function readme
*/
void
readme
()
{
std
::
cout
<<
" Usage: ./SURF_descriptor <img1> <img2>"
<<
std
::
endl
;
}
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