//allocate buffer
 BYTE* pRgb32Buffer = new BYTE[width*height* 4];
 //create paint device
 QImage img = QImage(pRgb32Buffer , width, height, getStride(width, pixelFormat), QImage::Format_RGB32);
 //do some drawing on image (works!) 
 QPainter painter(&img);
 painter.drawText(10, 50, QString("some text"));
 //mirrore image (doesn't mirror the orignal buffer!!!)
 img = img.mirrored(false,true);
 //doesn't work either
 //QImage mirrored = img.mirrored();
 //img = mirrored;
 //mirrored.detach();