Capture a frame (image) from a video playing in a QT GUI - c++

Question

I have written a simple video player GUI code in QT. The GUI allows the user to browse the local files and select a video for playing in the GUI. The GUI also has options for 'play', 'pause' and 'stop' to apply to the video selected.
I want to add another button 'Capture', that captures the current frame of the video that is being played, and displays this captured image next to the video (The video should should get paused at this point).
I looked into the documentation of QT, specifically: this and this. But I am still not able to understand how to implement this in my case.
Kindly guide.
My code so far is as follows:
#include "qtwidgetsapplication4.h"
#include <iostream>
QtWidgetsApplication4::QtWidgetsApplication4(QWidget *parent)
: QMainWindow(parent)
{
ui.setupUi(this);
player = new QMediaPlayer(this);
vw = new QVideoWidget(this);
player->setVideoOutput(vw);
this->setCentralWidget(vw);
}
void QtWidgetsApplication4::on_actionOpen_triggered() {
QString filename = QFileDialog::getOpenFileName(this, "Open a File", "", "Video File (*.*)");
on_actionStop_triggered();
player->setSource(QUrl::fromLocalFile(filename));
on_actionPlay_triggered();
qDebug("Error Message in actionOpen");
qDebug()<<player->mediaStatus();
}
void QtWidgetsApplication4::on_actionPlay_triggered() {
player->play();
ui.statusBar->showMessage("Playing");
qDebug("Error Message in actionPlay");
qDebug() << player->mediaStatus();
}
void QtWidgetsApplication4::on_actionPause_triggered() {
player->pause();
ui.statusBar->showMessage("Paused...");
qDebug("Error Message in actionPause");
qDebug() << player->mediaStatus();
}
void QtWidgetsApplication4::on_actionStop_triggered() {
player->stop();
ui.statusBar->showMessage("Stopped");
qDebug("Error Message in actionStop");
qDebug() << player->mediaStatus();
}

Answer 1

You can use QVideoProbe to capture QVideoFrame. Instantiate and connect videoFrameProbed signal to your slot before pausing video. Convert QVideoFrame to QImage in this slot using frame data.
QImage::Format imageFormat = QVideoFrame::imageFormatFromPixelFormat(frame.pixelFormat());
QImage image(frame.bits(), frame.width(), frame.height(), imageFormat);
Take a look at player example for reference. It uses QVideoProbe to calculate histogram of current frame.