试试下面的代码:
QPainter painter;
painter.begin(pixmap);
painter.setRenderHint(QPainter::Antialiasing, true);
pixmap->fill(Qt::white);
QRectF target((event->x()-myFrame->x()-pixmap->width()/2), -(event->y()-myFrame->y()-pixmap->height()/2), 40.0, 40.0);
QRectF source(0.0, 0.0, 40.0, 40.0);
painter.drawImage(target, *markStart, source);
painter.end();