title: PyQt/Qt: How to stretch an image in Qlabel widget?
body: <p>I want to display an image in my app. I use QtDesigner to design UI, then use pyqt to coding. The problem is the image that will be shown is lager than the widget size on the UI. I refer to offical demo:
  <a href="http://doc.qt.nokia.com/4.7-snapshot/widgets-imageviewer.html" rel="noreferrer">QT - Widget Image Viewer Demo</a></p>
  
  <p>add imagelabel and scrollArea, code as follows:</p>
  
  <pre><code>---- UI init ----
  self.label = QtGui.QLabel(self.centralwidget)
  self.label.setGeometry(QtCore.QRect(40, 140, 361, 511))
  self.label.setSizePolicy(QtGui.QSizePolicy.Preferred,QtGui.QSizePolicy.Preferred)
  self.label.setObjectName(_fromUtf8("label"))
  self.scrollArea = QtGui.QScrollArea(self.centralwidget)
  self.scrollArea.setGeometry(QtCore.QRect(40, 140, 361, 511))
  self.scrollArea.setWidget(self.label)
  self.scrollArea.setObjectName(_fromUtf8("scrollArea"))
  
  ---- function ----
  filename = "./Penguins.jpg"
  image = QtGui.QImage(filename)
  pp = QtGui.QPixmap.fromImage(image)
  lbl = QtGui.QLabel(self.label)
  lbl.setPixmap(pp)
  self.scrollArea.setWidgetResizable(True)
  lbl.show()
  </code></pre>
  
  <p>but it doesn't stretch the image, even no scroll bar appear!</p>