tutorial-matching-keypoint-homography.cpp

#include <visp3/core/vpPixelMeterConversion.h>
#include <visp3/gui/vpDisplayOpenCV.h>
#include <visp3/io/vpVideoReader.h>
#include <visp3/vision/vpHomography.h>
#include <visp3/vision/vpKeyPoint.h>

int main(int argc, const char **argv)
{
#if (VISP_HAVE_OPENCV_VERSION >= 0x020101)
  int method = 0;

  if (argc > 1)
    method = atoi(argv[1]);

  if (method == 0)
    std::cout << "Uses Ransac to estimate the homography" << std::endl;
  else
    std::cout << "Uses a robust scheme to estimate the homography" << std::endl;

  vpImage<unsigned char> I;

  vpVideoReader reader;
  reader.setFileName("video-postcard.mp4");
  reader.acquire(I);

  const std::string detectorName = "ORB";
  const std::string extractorName = "ORB";
  // Hamming distance must be used with ORB
  const std::string matcherName = "BruteForce-Hamming";
  vpKeyPoint::vpFilterMatchingType filterType = vpKeyPoint::ratioDistanceThreshold;
  vpKeyPoint keypoint(detectorName, extractorName, matcherName, filterType);
  keypoint.buildReference(I);

  vpImage<unsigned char> Idisp;
  Idisp.resize(I.getHeight(), 2 * I.getWidth());
  Idisp.insert(I, vpImagePoint(0, 0));
  Idisp.insert(I, vpImagePoint(0, I.getWidth()));

  vpDisplayOpenCV d(Idisp, 0, 0, "Homography from matched keypoints");
  vpDisplay::display(Idisp);
  vpDisplay::flush(Idisp);

  vpImagePoint corner_ref[4];
  corner_ref[0].set_ij(115, 64);
  corner_ref[1].set_ij(83, 253);
  corner_ref[2].set_ij(282, 307);
  corner_ref[3].set_ij(330, 72);
  for (unsigned int i = 0; i < 4; i++) {
    vpDisplay::displayCross(Idisp, corner_ref[i], 12, vpColor::red);
  }
  vpDisplay::flush(Idisp);

  vpCameraParameters cam(840, 840, I.getWidth() / 2, I.getHeight() / 2);

  vpHomography curHref;

  while (!reader.end()) {
    reader.acquire(I);
    Idisp.insert(I, vpImagePoint(0, I.getWidth()));
    vpDisplay::display(Idisp);
    vpDisplay::displayLine(Idisp, vpImagePoint(0, I.getWidth()), vpImagePoint(I.getHeight(), I.getWidth()),
                           vpColor::white, 2);

    unsigned int nbMatch = keypoint.matchPoint(I);
    std::cout << "Nb matches: " << nbMatch << std::endl;

    std::vector<vpImagePoint> iPref(nbMatch),
        iPcur(nbMatch); // Coordinates in pixels (for display only)
    std::vector<double> mPref_x(nbMatch), mPref_y(nbMatch);
    std::vector<double> mPcur_x(nbMatch), mPcur_y(nbMatch);
    std::vector<bool> inliers(nbMatch);

    for (unsigned int i = 0; i < nbMatch; i++) {
      keypoint.getMatchedPoints(i, iPref[i], iPcur[i]);
      vpPixelMeterConversion::convertPoint(cam, iPref[i], mPref_x[i], mPref_y[i]);
      vpPixelMeterConversion::convertPoint(cam, iPcur[i], mPcur_x[i], mPcur_y[i]);
    }

    try {
      double residual;
      if (method == 0)
        vpHomography::ransac(mPref_x, mPref_y, mPcur_x, mPcur_y, curHref, inliers, residual,
                             (unsigned int)(mPref_x.size() * 0.25), 2.0 / cam.get_px(), true);
      else
        vpHomography::robust(mPref_x, mPref_y, mPcur_x, mPcur_y, curHref, inliers, residual, 0.4, 4, true);
    } catch (...) {
      std::cout << "Cannot compute homography from matches..." << std::endl;
    }


    vpImagePoint corner_cur[4];
    for (int i = 0; i < 4; i++) {
      corner_cur[i] = vpHomography::project(cam, curHref, corner_ref[i]);
    }

    vpImagePoint offset(0, I.getWidth());
    for (int i = 0; i < 4; i++) {
      vpDisplay::displayLine(Idisp, corner_cur[i] + offset, corner_cur[(i + 1) % 4] + offset, vpColor::blue, 3);
    }

    for (unsigned int i = 0; i < nbMatch; i++) {
      if (inliers[i] == true)
        vpDisplay::displayLine(Idisp, iPref[i], iPcur[i] + offset, vpColor::green);
      else
        vpDisplay::displayLine(Idisp, iPref[i], iPcur[i] + offset, vpColor::red);
    }

    vpDisplay::flush(Idisp);

    if (vpDisplay::getClick(Idisp, false))
      break;
  }

  vpDisplay::getClick(Idisp);
#else
  (void)argc;
  (void)argv;
#endif
  return 0;
}