Visual Servoing Platform  version 3.6.1 under development (2024-05-21)
#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)
int method = 0;
if (argc > 1)
method = atoi(argv[1]);
if (method == 0)
std::cout << "Uses Ransac to estimate the homography" << std::endl;
std::cout << "Uses a robust scheme to estimate the homography" << std::endl;
vpVideoReader reader;
const std::string detectorName = "ORB";
const std::string extractorName = "ORB";
// Hamming distance must be used with ORB
const std::string matcherName = "BruteForce-Hamming";
vpKeyPoint keypoint(detectorName, extractorName, matcherName, filterType);
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");
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);
vpCameraParameters cam(840, 840, I.getWidth() / 2, I.getHeight() / 2);
vpHomography curHref;
while (!reader.end()) {
Idisp.insert(I, vpImagePoint(0, I.getWidth()));
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);
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);
vpDisplay::displayLine(Idisp, iPref[i], iPcur[i] + offset, vpColor::red);
if (vpDisplay::getClick(Idisp, false))
void getMatchedPoints(unsigned int index, vpImagePoint &referencePoint, vpImagePoint &currentPoint)
Generic class defining intrinsic camera parameters.
static const vpColor white
Definition: vpColor.h:206
static const vpColor red
Definition: vpColor.h:211
static const vpColor blue
Definition: vpColor.h:217
static const vpColor green
Definition: vpColor.h:214
The vpDisplayOpenCV allows to display image using the OpenCV library. Thus to enable this class OpenC...
static bool getClick(const vpImage< unsigned char > &I, bool blocking=true)
static void display(const vpImage< unsigned char > &I)
static void displayLine(const vpImage< unsigned char > &I, const vpImagePoint &ip1, const vpImagePoint &ip2, const vpColor &color, unsigned int thickness=1, bool segment=true)
static void displayCross(const vpImage< unsigned char > &I, const vpImagePoint &ip, unsigned int size, const vpColor &color, unsigned int thickness=1)
static void flush(const vpImage< unsigned char > &I)
Implementation of an homography and operations on homographies.
Definition: vpHomography.h:168
static vpImagePoint project(const vpCameraParameters &cam, const vpHomography &bHa, const vpImagePoint &iPa)
static void robust(const std::vector< double > &xb, const std::vector< double > &yb, const std::vector< double > &xa, const std::vector< double > &ya, vpHomography &aHb, std::vector< bool > &inliers, double &residual, double weights_threshold=0.4, unsigned int niter=4, bool normalization=true)
static bool ransac(const std::vector< double > &xb, const std::vector< double > &yb, const std::vector< double > &xa, const std::vector< double > &ya, vpHomography &aHb, std::vector< bool > &inliers, double &residual, unsigned int nbInliersConsensus, double threshold, bool normalization=true)
Class that defines a 2D point in an image. This class is useful for image processing and stores only ...
Definition: vpImagePoint.h:82
void set_ij(double ii, double jj)
Definition: vpImagePoint.h:316
unsigned int getWidth() const
Definition: vpImage.h:245
void resize(unsigned int h, unsigned int w)
resize the image : Image initialization
Definition: vpImage.h:798
void insert(const vpImage< Type > &src, const vpImagePoint &topLeft)
Definition: vpImage.h:1609
unsigned int getHeight() const
Definition: vpImage.h:184
Class that allows keypoints detection (and descriptors extraction) and matching thanks to OpenCV libr...
Definition: vpKeyPoint.h:212
unsigned int matchPoint(const vpImage< unsigned char > &I)
Definition: vpKeyPoint.h:216
@ ratioDistanceThreshold
Definition: vpKeyPoint.h:221
unsigned int buildReference(const vpImage< unsigned char > &I)
Definition: vpKeyPoint.cpp:189
static void convertPoint(const vpCameraParameters &cam, const double &u, const double &v, double &x, double &y)
Class that enables to manipulate easily a video file or a sequence of images. As it inherits from the...
void acquire(vpImage< vpRGBa > &I)
void setFileName(const std::string &filename)