 QPalette pal = palette();
QPalette pal = palette();  pal.setColor(QPalette::Background, QColor(0x00,0xff,0x00,0x00));
pal.setColor(QPalette::Background, QColor(0x00,0xff,0x00,0x00));  setPalette(pal);
setPalette(pal); setAttribute(Qt::WA_TranslucentBackground, true);
setAttribute(Qt::WA_TranslucentBackground, true); setWindowOpacity(0.7)
setWindowOpacity(0.7) void TestWindow::paintEvent( QPaintEvent* )
void TestWindow::paintEvent( QPaintEvent* )  {
{  QPainter p(this);
                QPainter p(this);  p.setCompositionMode( QPainter::CompositionMode_Clear );
                p.setCompositionMode( QPainter::CompositionMode_Clear );  p.fillRect( 10, 10, 300, 300, Qt::SolidPattern );
                p.fillRect( 10, 10, 300, 300, Qt::SolidPattern );  }
} 原文:http://www.cnblogs.com/findumars/p/4746462.html