An example program with homography decomposition.
#include <iostream>
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:
}
}
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;
}
void computeC2MC1(
const Mat &R1,
const Mat &tvec1,
const Mat &R2,
const Mat &tvec2,
{
tvec_1to2 = R2 * (-R1.t()*tvec1) + tvec2; }
void decomposeHomography(
const string &img1Path,
const string &img2Path,
const Size &patternSize,
const float squareSize, const string &intrinsicsPath)
{
vector<Point2f> corners1, corners2;
if (!found1 || !found2)
{
cout << "Error, cannot find the chessboard corners in both images." << endl;
return;
}
vector<Point3f> objectPoints;
calcChessboardCorners(patternSize, squareSize, objectPoints);
Mat cameraMatrix, distCoeffs; fs["camera_matrix"] >> cameraMatrix;
fs["distortion_coefficients"] >> distCoeffs;
solvePnP(objectPoints, corners1, cameraMatrix, distCoeffs, rvec1, tvec1); solvePnP(objectPoints, corners2, cameraMatrix, distCoeffs, rvec2, tvec2); computeC2MC1(R1, tvec1, R2, tvec2, R_1to2, t_1to2);
Mat origin1 = R1*origin + tvec1; double d_inv1 = 1.0 / normal1.dot(origin1); 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); vector<Mat> Rs_decomp, ts_decomp, normals_decomp;
cout << "Decompose homography matrix computed from the camera displacement:" << endl << endl;
for (int i = 0; i < solutions; i++)
{
double factor_d1 = 1.0 / d_inv1;
cout << "Solution " << i << ":" << endl;
cout << "rvec from homography decomposition: " << rvec_decomp.t() << endl; cout << "rvec from camera displacement: " << rvec_1to2.t() << endl; cout << "tvec from homography decomposition: " << ts_decomp[i].t() << " and scaled by d: " << factor_d1 * ts_decomp[i].t() << endl; cout << "tvec from camera displacement: " << t_1to2.t() << endl; cout << "plane normal from homography decomposition: " << normals_decomp[i].t() << endl; cout << "plane normal at camera 1 pose: " << normal1.t() << endl << endl; }
cout << "Decompose homography matrix estimated by findHomography():" << endl << endl;
for (int i = 0; i < solutions; i++)
{
double factor_d1 = 1.0 / d_inv1;
cout << "Solution " << i << ":" << endl;
cout << "rvec from homography decomposition: " << rvec_decomp.t() << endl; cout << "rvec from camera displacement: " << rvec_1to2.t() << endl; cout << "tvec from homography decomposition: " << ts_decomp[i].t() << " and scaled by d: " << factor_d1 * ts_decomp[i].t() << endl; cout << "tvec from camera displacement: " << t_1to2.t() << endl; cout << "plane normal from homography decomposition: " << normals_decomp[i].t() << endl; cout << "plane normal at camera 1 pose: " << normal1.t() << endl << endl; }
}
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[])
{
if ( parser.has("help") ) {
parser.about( "Code for homography tutorial.\n" "Example 4: decompose the homography matrix.\n" );
return 0;
}
Size patternSize(parser.get<int>("width"), parser.get<int>("height")); float squareSize = (float) parser.get<double>("square_size"); decomposeHomography(parser.get<String>("image1"), patternSize, squareSize,
return 0;
}