pyqgis - NameError: name 'QImage' is not defined

Traceback (most recent call last):
  File "", line 1, in 
  File "F:/QGIS/bin/test.py", line 6, in 
    img = QImage(QSize(800,600), QImage.Format_ARGB32_Premultiplied)
NameError: name 'QImage' is not defined

I encountered this error when I was trying for Map Rendering and Printing on python console given in QGIS.