Visual Servoing Platform  version 3.6.1 under development (2024-07-23)
#include <visp3/core/vpConfig.h>
#include <visp3/detection/vpDetectorFace.h>
#include <visp3/gui/vpDisplayGDI.h>
#include <visp3/gui/vpDisplayOpenCV.h>
#include <visp3/gui/vpDisplayX.h>
#include <visp3/sensor/vpV4l2Grabber.h>
#include <opencv2/videoio.hpp>
int main(int argc, const char *argv[])
using namespace VISP_NAMESPACE_NAME;
try {
std::string opt_face_cascade_name = "./haarcascade_frontalface_alt.xml";
unsigned int opt_device = 0;
unsigned int opt_scale = 2; // Default value is 2 in the constructor. Turn
// it to 1 to avoid subsampling
for (int i = 0; i < argc; i++) {
if (std::string(argv[i]) == "--haar")
opt_face_cascade_name = std::string(argv[i + 1]);
else if (std::string(argv[i]) == "--device")
opt_device = (unsigned int)atoi(argv[i + 1]);
else if (std::string(argv[i]) == "--scale")
opt_scale = (unsigned int)atoi(argv[i + 1]);
else if (std::string(argv[i]) == "--help") {
std::cout << "Usage: " << argv[0]
<< " [--haar <haarcascade xml filename>] [--device <camera "
"device>] [--scale <subsampling factor>] [--help]"
<< std::endl;
vpImage<unsigned char> I; // for gray images
#if defined(VISP_HAVE_V4L2)
std::ostringstream device;
device << "/dev/video" << opt_device;
g.setScale(opt_scale); // Default value is 2 in the constructor. Turn it
// to 1 to avoid subsampling
#elif defined(HAVE_OPENCV_VIDEOIO)
cv::VideoCapture cap(opt_device); // open the default camera
#if (VISP_HAVE_OPENCV_VERSION >= 0x030000)
int width = (int)cap.get(cv::CAP_PROP_FRAME_WIDTH);
int height = (int)cap.get(cv::CAP_PROP_FRAME_HEIGHT);
cap.set(cv::CAP_PROP_FRAME_WIDTH, width / opt_scale);
cap.set(cv::CAP_PROP_FRAME_HEIGHT, height / opt_scale);
int width = cap.get(CV_CAP_PROP_FRAME_WIDTH);
int height = cap.get(CV_CAP_PROP_FRAME_HEIGHT);
cap.set(CV_CAP_PROP_FRAME_WIDTH, width / opt_scale);
cap.set(CV_CAP_PROP_FRAME_HEIGHT, height / opt_scale);
if (!cap.isOpened()) { // check if we succeeded
std::cout << "Failed to open the camera" << std::endl;
cv::Mat frame;
cap >> frame; // get a new frame from camera
#if defined(VISP_HAVE_X11)
vpDisplayX d(I);
#elif defined(VISP_HAVE_GDI)
#elif defined(HAVE_OPENCV_HIGHGUI)
vpDisplay::setTitle(I, "ViSP viewer");
vpDetectorFace face_detector;
while (1) {
double t = vpTime::measureTimeMs();
#if defined(VISP_HAVE_V4L2)
bool face_found = face_detector.detect(I);
cap >> frame; // get a new frame from camera
bool face_found = face_detector.detect(frame); // We pass frame to avoid an internal image conversion
if (face_found) {
std::ostringstream text;
text << "Found " << face_detector.getNbObjects() << " face(s)";
vpDisplay::displayText(I, 10, 10, text.str(), vpColor::red);
for (size_t i = 0; i < face_detector.getNbObjects(); i++) {
vpRect bbox = face_detector.getBBox(i);
vpDisplay::displayText(I, (int)bbox.getTop() - 10, (int)bbox.getLeft(),
"Message: \"" + face_detector.getMessage(i) + "\"", vpColor::red);
vpDisplay::displayText(I, (int)I.getHeight() - 25, 10, "Click to quit...", vpColor::red);
if (vpDisplay::getClick(I, false)) // a click to exit
std::cout << "Loop time: " << vpTime::measureTimeMs() - t << " ms" << std::endl;
catch (const vpException &e) {
std::cout << e.getMessage() << std::endl;
static const vpColor red
Definition: vpColor.h:217
static const vpColor green
Definition: vpColor.h:220
vpRect getBBox(size_t i) const
size_t getNbObjects() const
std::vector< std::string > & getMessage()
void setCascadeClassifierFile(const std::string &filename)
bool detect(const vpImage< unsigned char > &I) VP_OVERRIDE
Display for windows using GDI (available on any windows 32 platform).
Definition: vpDisplayGDI.h:130
The vpDisplayOpenCV allows to display image using the OpenCV library. Thus to enable this class OpenC...
Use the X11 console to display images on unix-like OS. Thus to enable this class X11 should be instal...
Definition: vpDisplayX.h:135
static bool getClick(const vpImage< unsigned char > &I, bool blocking=true)
static void display(const vpImage< unsigned char > &I)
static void setTitle(const vpImage< unsigned char > &I, const std::string &windowtitle)
static void flush(const vpImage< unsigned char > &I)
static void displayRectangle(const vpImage< unsigned char > &I, const vpImagePoint &topLeft, unsigned int width, unsigned int height, const vpColor &color, bool fill=false, unsigned int thickness=1)
static void displayText(const vpImage< unsigned char > &I, const vpImagePoint &ip, const std::string &s, const vpColor &color)
error that can be emitted by ViSP classes.
Definition: vpException.h:60
const char * getMessage() const
Definition: vpException.cpp:65
static void convert(const vpImage< unsigned char > &src, vpImage< vpRGBa > &dest)
unsigned int getHeight() const
Definition: vpImage.h:181
Defines a rectangle in the plane.
Definition: vpRect.h:79
double getLeft() const
Definition: vpRect.h:173
double getTop() const
Definition: vpRect.h:192
Class that is a wrapper over the Video4Linux2 (V4L2) driver.
void setScale(unsigned scale=vpV4l2Grabber::DEFAULT_SCALE)
void setDevice(const std::string &devname)
void acquire(vpImage< unsigned char > &I)
VISP_EXPORT double measureTimeMs()