Taking screenshot of a specific window - C++ / Qt

Question

In Qt, how do I take a screenshot of a specific window (i.e. suppose I had Notepad up and I wanted to take a screenshot of the window titled "Untitled - Notepad")? In their screenshot example code, they show how to take a screenshot of the entire desktop:

originalPixmap = QPixmap::grabWindow(QApplication::desktop()->winId());

How would I get the winId() for a specific window (assuming I knew the window's title) in Qt?

Thanks

score 6 · Accepted Answer · answered Nov 21 '09 at 01:46

6

I'm pretty sure that's platform-specific. winIds are HWNDs on Windows, so you could call FindWindow(NULL, "Untitled - Notepad") in the example you gave.

answered Nov 21 '09 at 01:46

ChrisV

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score 2 · Answer 2 · answered Sep 30 '11 at 22:34

2

Look at QDesktopWidget class. It's inherited from QWidget so there is literally no problem of taking screenshot:

QPixmap pm(QDesktopWidget::screenGeometry().size());
QDesktopWidget::screen().render(&pm); // pm now contains screenshot

answered Sep 30 '11 at 22:34

GreenScape

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1

For version `4.8` I had to make little changes to your snippet. Mainly: create an object of type `QDesktopWidget` to call `screenGeometry()` and `screen()`, and change `screen().render()` to `screen()->render()`, as `screen()` returns a `QWidget*`. – Adri C.S. Apr 22 '15 at 10:38

score 1 · Answer 3 · answered May 24 '10 at 19:28

1

Also look at WindowFromPoint and EnumChildWindows. The latter could allow you to prompt the user to disambiguate if you had multiple windows with the same title.

answered May 24 '10 at 19:28

Jake Petroules

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score 1 · Answer 4 · answered Jun 04 '15 at 17:31

1

Have a look at Screenshot example

In short:

QScreen *screen = QGuiApplication::primaryScreen();
if (screen)
    QPixmap originalPixmap = screen->grabWindow(0);

answered Jun 04 '15 at 17:31

Nya

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This answer is not about "Taking screenshot of a specific window". This is about taking screenshot of whole screen. – Alok Aug 18 '21 at 11:07

score -1 · Answer 5 · answered Apr 28 '14 at 20:21

Although this has already been answered, just for the sake of completeness, I'll add to Trevor Boyd Smith's post (see above) a code-snippet example:

void MainWindow::on_myButton_GUI_Screeshot_clicked()
{
    QPixmap qPixMap = QPixmap::grabWidget(this);  // *this* is window pointer, the snippet     is in the mainwindow.cpp file

    QImage qImage = qPixMap.toImage();

    cv::Mat GUI_SCREENSHOT = cv::Mat(         qImage.height(),
                                              qImage.width(), CV_8UC4,
                                      (uchar*)qImage.bits(),
                                              qImage.bytesPerLine()  );

    cv::imshow("GUI_SCREENSHOT",GUI_SCREENSHOT);
}

Taking screenshot of a specific window - C++ / Qt

5 Answers5

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