Index: src/gui/qgsmapcanvasmap.cpp
===================================================================
--- src/gui/qgsmapcanvasmap.cpp	(revision 9268)
+++ src/gui/qgsmapcanvasmap.cpp	(working copy)
@@ -49,6 +49,7 @@
 void QgsMapCanvasMap::resize( QSize size )
 {
   mPixmap = QPixmap( size );
+  mImage = QImage( size, QImage::Format_RGB32 );	// temporary image - build it here so it is available when switching from QPixmap to QImage rendering
   mCanvas->mapRenderer()->setOutputSize( size, mPixmap.logicalDpiX() );
 }
 
@@ -68,8 +69,6 @@
   if ( mUseQImageToRender )
   {
     // use temporary image for rendering
-    mImage = QImage( boundingRect().size().toSize(), QImage::Format_RGB32 );
-
     mImage.fill( mBgColor.rgb() );
 
     QPainter paint;
Index: src/gui/qgsmapcanvas.cpp
===================================================================
--- src/gui/qgsmapcanvas.cpp	(revision 9268)
+++ src/gui/qgsmapcanvas.cpp	(working copy)
@@ -160,6 +160,7 @@
 void QgsMapCanvas::useImageToRender( bool theFlag )
 {
   mMap->useImageToRender( theFlag );
+  refresh();	// redraw the map on change - prevents black map view
 }
 
 QgsMapCanvasMap* QgsMapCanvas::map()