How to get DC from QPainter in windows?

[qingyun]

I have a very very strange question, it is very urgent, hope anybody can help me!

I want to get a native DC from QPainter. I tried like this:
QPaintEngine* pe = painter.paintEngine();
HDC dc = pe->getDC();

This works fine if this painter is from a widget, like:
QPainter painter(this); //"this" is widget
But my painter is from a QPixmap:
QPixmap pix(w, h);
QPainter painter(&pix);

This always fails!!! The DC in paintEngine() is always 0!

Can anybody help me?

Thanks!