Check the corresponding tutorial for more details
#include <iostream>
double getOrientation(
const vector<Point> &,
Mat&);
{
double angle = atan2( (double) p.y - q.y, (double) p.x - q.x ); double hypotenuse = sqrt( (double) (p.y - q.y) * (p.y - q.y) + (p.x - q.x) * (p.x - q.x));
q.x = (int) (p.x - scale * hypotenuse * cos(angle)); q.y = (int) (p.y - scale * hypotenuse * sin(angle));
}
double getOrientation(
const vector<Point> &pts,
Mat &img)
{
int sz = static_cast<int>(pts.size());
for (int i = 0; i < data_pts.rows; i++) {
data_pts.at<double>(i, 0) = pts[i].x; data_pts.at<double>(i, 1) = pts[i].y; }
PCA pca_analysis(data_pts, Mat(), PCA::DATA_AS_ROW);
Point cntr = Point(static_cast<int>(pca_analysis.mean.at<double>(0, 0)), static_cast<int>(pca_analysis.mean.at<double>(0, 1)));
vector<Point2d> eigen_vecs(2);
vector<double> eigen_val(2);
for (int i = 0; i < 2; i++)
{
eigen_vecs[i] = Point2d(pca_analysis.eigenvectors.at<double>(i, 0), pca_analysis.eigenvectors.at<double>(i, 1));
eigen_val[i] = pca_analysis.eigenvalues.at<double>(i);
}
Point p1 = cntr + 0.02 * Point(static_cast<int>(eigen_vecs[0].x * eigen_val[0]), static_cast<int>(eigen_vecs[0].y * eigen_val[0])); Point p2 = cntr - 0.02 * Point(static_cast<int>(eigen_vecs[1].x * eigen_val[1]), static_cast<int>(eigen_vecs[1].y * eigen_val[1])); double angle = atan2(eigen_vecs[0].y, eigen_vecs[0].x); return angle;
}
int main(int argc, char** argv)
{
parser.about( "This program demonstrates how to use OpenCV PCA to extract the orientation of an object.\n" );
parser.printMessage();
{
cout << "Problem loading image!!!" << endl;
return EXIT_FAILURE;
}
vector<vector<Point> > contours;
for (size_t i = 0; i < contours.size(); i++)
{
if (area < 1e2 || 1e5 < area) continue;
getOrientation(contours[i], src);
}
return EXIT_SUCCESS;
}