screenshot of a qt application from inside the app

Question

I am trying to capture a screenshot of my application within the application. Its a Qt-based application. Is anyone aware of how to do this? Any suggestions are very welcome.

CV

Answer 1

You can tell any QWidget (including your QMainWindow) to render itself off-screen: http://developer.qt.nokia.com/doc/qt-4.8/qwidget.html#render

Technically this is not a screenshot as it renders the widget explicitely for this purpose instead of capturing what is seen on-screen. For almost any purpose it doesn't matter.

If you have a GL widget, you can/must instead use grabFramebuffer() which has the advantage of capturing what is seen on the screen.

Answer 2

QPixmap lets you do a window grab if you have the ID. My references are for PyQt but I'm sure you can make the adjustments:

How to get RGB values of QPixmap or QImage pixel - Qt, PyQt

http://www.riverbankcomputing.co.uk/static/Docs/PyQt4/html/qpixmap.html#grabWindow

Answer 3

With this example you could get all your widget screen. You could attach this method to any key press or signal, as you prefer, to get successive screenshot.

MyClass::screenshot()
{
    QWidget *w = QApplication::activeWindow();
    if(w) {
        static int count = 0;
        QPixmap p = QPixmap::grabWidget(w);
        p.save(QString("/your/path/screenshot%1.png").arg(count));
        count++;
    }
}

Answer 4

In modern QT 5+ it can be done like that:

void MainWindow::takeScreenshot(const QString screenshotFileName)
{
    if(isActiveWindow())
    {
        auto grabbedScreenshot = QWidget::grab();
        grabbedScreenshot.save(screenshotFileName);
    }
}