Question

Is there a way to capture the whole screen generated by QML? Something like copy drawing buffer in OpenGL or DirectX. The idea is to capture the output of the whole screen then do image subtraction with a camera feed of the screen so we can detect objects on top of the screen.

Thank you.

Answer 1

I think you want QPixmap::grabWindow(...), but I’m afraid I don’t use QML so I’m not certain how you would go about obtaining the pixmap or then using it.

Looking at some of the Qt documentation suggests that subclassing QDeclarativeImageProvider would be a good place to start. Something like:

class cScreenGrabber : public QDeclarativeImageProvider
{
public:
  cScreenGrabber ()
    : QDeclarativeImageProvider(QDeclarativeImageProvider::Pixmap) { }

  QPixmap requestPixmap(const QString &id, QSize *size, const QSize &requestedSize)
  {
    QWidget *ViewWidget = //get the widget containing your view//
    QPixmap Pixmap = QPixmap::grabWindow(ViewWidget.winId(), 0, 0,
                                         requestedSize.width() > 0 ? requestedSize.width() : -1,
                                         requestedSize.height() > 0 ? requestedSize.height() : -1);

    if (size)
      *size = QSize(Pixmap.width(), Pixmap.height());       

    return Pixmap;
  }
};