1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
|
#include <iostream>
#include <opencv2/core.hpp>
#include <opencv2/imgproc.hpp>
#include <opencv2/highgui.hpp>
#include <opencv2/calib3d.hpp>
using namespace std;
using namespace cv;
namespace
{
enum Pattern { CHESSBOARD, CIRCLES_GRID, ASYMMETRIC_CIRCLES_GRID };
void calcChessboardCorners(Size boardSize, float squareSize, vector<Point3f>& corners, Pattern patternType = CHESSBOARD)
{
corners.resize(0);
switch (patternType)
{
case CHESSBOARD:
case CIRCLES_GRID:
for( int i = 0; i < boardSize.height; i++ )
for( int j = 0; j < boardSize.width; j++ )
corners.push_back(Point3f(float(j*squareSize),
float(i*squareSize), 0));
break;
case ASYMMETRIC_CIRCLES_GRID:
for( int i = 0; i < boardSize.height; i++ )
for( int j = 0; j < boardSize.width; j++ )
corners.push_back(Point3f(float((2*j + i % 2)*squareSize),
float(i*squareSize), 0));
break;
default:
CV_Error(Error::StsBadArg, "Unknown pattern type\n");
}
}
//! [compute-homography]
Mat computeHomography(const Mat &R_1to2, const Mat &tvec_1to2, const double d_inv, const Mat &normal)
{
Mat homography = R_1to2 + d_inv * tvec_1to2*normal.t();
return homography;
}
//! [compute-homography]
Mat computeHomography(const Mat &R1, const Mat &tvec1, const Mat &R2, const Mat &tvec2,
const double d_inv, const Mat &normal)
{
Mat homography = R2 * R1.t() + d_inv * (-R2 * R1.t() * tvec1 + tvec2) * normal.t();
return homography;
}
//! [compute-c2Mc1]
void computeC2MC1(const Mat &R1, const Mat &tvec1, const Mat &R2, const Mat &tvec2,
Mat &R_1to2, Mat &tvec_1to2)
{
//c2Mc1 = c2Mo * oMc1 = c2Mo * c1Mo.inv()
R_1to2 = R2 * R1.t();
tvec_1to2 = R2 * (-R1.t()*tvec1) + tvec2;
}
//! [compute-c2Mc1]
void homographyFromCameraDisplacement(const string &img1Path, const string &img2Path, const Size &patternSize,
const float squareSize, const string &intrinsicsPath)
{
Mat img1 = imread( samples::findFile( img1Path ) );
Mat img2 = imread( samples::findFile( img2Path ) );
//! [compute-poses]
vector<Point2f> corners1, corners2;
bool found1 = findChessboardCorners(img1, patternSize, corners1);
bool found2 = findChessboardCorners(img2, patternSize, corners2);
if (!found1 || !found2)
{
cout << "Error, cannot find the chessboard corners in both images." << endl;
return;
}
vector<Point3f> objectPoints;
calcChessboardCorners(patternSize, squareSize, objectPoints);
FileStorage fs( samples::findFile( intrinsicsPath ), FileStorage::READ);
Mat cameraMatrix, distCoeffs;
fs["camera_matrix"] >> cameraMatrix;
fs["distortion_coefficients"] >> distCoeffs;
Mat rvec1, tvec1;
solvePnP(objectPoints, corners1, cameraMatrix, distCoeffs, rvec1, tvec1);
Mat rvec2, tvec2;
solvePnP(objectPoints, corners2, cameraMatrix, distCoeffs, rvec2, tvec2);
//! [compute-poses]
Mat img1_copy_pose = img1.clone(), img2_copy_pose = img2.clone();
Mat img_draw_poses;
drawFrameAxes(img1_copy_pose, cameraMatrix, distCoeffs, rvec1, tvec1, 2*squareSize);
drawFrameAxes(img2_copy_pose, cameraMatrix, distCoeffs, rvec2, tvec2, 2*squareSize);
hconcat(img1_copy_pose, img2_copy_pose, img_draw_poses);
imshow("Chessboard poses", img_draw_poses);
//! [compute-camera-displacement]
Mat R1, R2;
Rodrigues(rvec1, R1);
Rodrigues(rvec2, R2);
Mat R_1to2, t_1to2;
computeC2MC1(R1, tvec1, R2, tvec2, R_1to2, t_1to2);
Mat rvec_1to2;
Rodrigues(R_1to2, rvec_1to2);
//! [compute-camera-displacement]
//! [compute-plane-normal-at-camera-pose-1]
Mat normal = (Mat_<double>(3,1) << 0, 0, 1);
Mat normal1 = R1*normal;
//! [compute-plane-normal-at-camera-pose-1]
//! [compute-plane-distance-to-the-camera-frame-1]
Mat origin(3, 1, CV_64F, Scalar(0));
Mat origin1 = R1*origin + tvec1;
double d_inv1 = 1.0 / normal1.dot(origin1);
//! [compute-plane-distance-to-the-camera-frame-1]
//! [compute-homography-from-camera-displacement]
Mat homography_euclidean = computeHomography(R_1to2, t_1to2, d_inv1, normal1);
Mat homography = cameraMatrix * homography_euclidean * cameraMatrix.inv();
homography /= homography.at<double>(2,2);
homography_euclidean /= homography_euclidean.at<double>(2,2);
//! [compute-homography-from-camera-displacement]
//Same but using absolute camera poses instead of camera displacement, just for check
Mat homography_euclidean2 = computeHomography(R1, tvec1, R2, tvec2, d_inv1, normal1);
Mat homography2 = cameraMatrix * homography_euclidean2 * cameraMatrix.inv();
homography_euclidean2 /= homography_euclidean2.at<double>(2,2);
homography2 /= homography2.at<double>(2,2);
cout << "\nEuclidean Homography:\n" << homography_euclidean << endl;
cout << "Euclidean Homography 2:\n" << homography_euclidean2 << endl << endl;
//! [estimate-homography]
Mat H = findHomography(corners1, corners2);
cout << "\nfindHomography H:\n" << H << endl;
//! [estimate-homography]
cout << "homography from camera displacement:\n" << homography << endl;
cout << "homography from absolute camera poses:\n" << homography2 << endl << endl;
//! [warp-chessboard]
Mat img1_warp;
warpPerspective(img1, img1_warp, H, img1.size());
//! [warp-chessboard]
Mat img1_warp_custom;
warpPerspective(img1, img1_warp_custom, homography, img1.size());
imshow("Warped image using homography computed from camera displacement", img1_warp_custom);
Mat img_draw_compare;
hconcat(img1_warp, img1_warp_custom, img_draw_compare);
imshow("Warped images comparison", img_draw_compare);
Mat img1_warp_custom2;
warpPerspective(img1, img1_warp_custom2, homography2, img1.size());
imshow("Warped image using homography computed from absolute camera poses", img1_warp_custom2);
waitKey();
}
const char* params
= "{ help h | | print usage }"
"{ image1 | left02.jpg | path to the source chessboard image }"
"{ image2 | left01.jpg | path to the desired chessboard image }"
"{ intrinsics | left_intrinsics.yml | path to camera intrinsics }"
"{ width bw | 9 | chessboard width }"
"{ height bh | 6 | chessboard height }"
"{ square_size | 0.025 | chessboard square size }";
}
int main(int argc, char *argv[])
{
CommandLineParser parser(argc, argv, params);
if (parser.has("help"))
{
parser.about("Code for homography tutorial.\n"
"Example 3: homography from the camera displacement.\n");
parser.printMessage();
return 0;
}
Size patternSize(parser.get<int>("width"), parser.get<int>("height"));
float squareSize = (float) parser.get<double>("square_size");
homographyFromCameraDisplacement(parser.get<String>("image1"),
parser.get<String>("image2"),
patternSize, squareSize,
parser.get<String>("intrinsics"));
return 0;
}
|
