PaintEvent performance

[canol]

Hello, I am using Qt on pcDuino2 development board.

I need to do a fade in/out animation on an image displayed on a full HD display. I draw directly onto a fullscreen QWidget. What I do is that I update an alpha value in a thread and call update() through a signal to repaint the fullscreen widget. I first paint the pixmap then I fill a black rectangle with the new alpha value.

I try to repaint 30 FPS and the animation is very smooth on my laptop, but on pcDuino it is terrible (like 3 FPS or something). The paintEvent code is below, it is written using PySide but you can give advice using C++ as well.

I tried using QGraphicsScene but it didn't help either. So what advice would you give to make this a smooth animation with max performance?

@def paintEvent(self, event):
qp = QtGui.QPainter()
qp.begin(self)

    qp.drawPixmap(0, 0, self.my_pixmap)

    qp.fillRect(0,
                0,
                self.size().width(),
                self.size().height(),
                QtGui.QColor(0, 0, 0, round(self.fade_alpha)))

    qp.end()@