This is the way to do it for Qt 4 (QtGui):
QImage image(QPixmap::fromWinHBITMAP(hBitmap).toImage());
This is the way to do it for Qt 5 (QtWinExtras):
QPixmap pixmap = QtWin::fromHBITMAP(hBitmap);
QImage image = pixmap.toImage();
// or
QtWin::imageFromHBITMAP(hdc, hBitmap, width, height)