Added documentation on exporting

doc/source/exporting.rst

+Exporting
+=========
+
+PyQtGraph provides a variety of export formats for all 2D graphics. For 3D graphics, see `Exporting 3D Graphics`_ below.
+
+Exporting from the GUI
+----------------------
+
+Any 2D graphics can be exported by right-clicking on the graphic, then selecting 'export' from the context menu. 
+This will display the export dialog in which the user must:
+
+#. Select an item (or the entire scene) to export. Selecting an item will cause the item to be hilighted in the original 
+   graphic window (but this hilight will not be displayed in the exported file). 
+#. Select an export format.
+#. Change any desired export options.
+#. Click the 'export' button.
+
+Export Formats
+--------------
+
+* Image - PNG is the default format. The exact set of image formats supported will depend on your Qt libraries. However, 
+  common formats such as PNG, JPG, and TIFF are almost always available. 
+* SVG - Graphics exported as SVG are targeted to work as well as possible with both Inkscape and 
+  Adobe Illustrator. For high quality SVG export, please use PyQtGraph version 0.9.3 or later.
+  This is the preferred method for generating publication graphics from PyQtGraph.
+* CSV - Exports plotted data as CSV. This exporter _only_ works if a PlotItem is selected for export.
+* Matplotlib - This exporter opens a new window and attempts to re-plot the
+  data using matplotlib (if available). Note that some graphic features are either not implemented
+  for this exporter or not available in matplotlib. This exporter _only_ works if a PlotItem is selected
+  for export.
+* Printer - Exports to the operating system's printing service. This exporter is provided for completeness, 
+  but is not well supported due to problems with Qt's printing system.
+
+
+
+Exporting from the API
+----------------------
+
+To export a file programatically, follow this example::
+
+    import pyqtgraph as pg
+    
+    # generate something to export
+    plt = pg.plot([1,5,2,4,3])
+
+    # create an exporter instance, as an argument give it
+    # the item you wish to export
+    exporter = pg.exporters.ImageExporter.ImageExporter(plt.plotItem)
+
+    # set export parameters if needed
+    exporter.parameters()['width'] = 100   # (note this also affects height parameter)
+    
+    # save to file
+    exporter.export('fileName.png')
+    
+
+Exporting 3D Graphics
+---------------------
+
+The exporting functionality described above is not yet available for 3D graphics. However, it is possible to 
+generate an image from a GLViewWidget by using QGLWidget.grabFrameBuffer or QGLWidget.renderPixmap::
+
+    glview.grabFrameBuffer().save('fileName.png')
+
+See the Qt documentation for more information. 
+
+    

doc/source/index.rst

@@ -20,6 +20,7 @@ Contents:
     3dgraphics
     style
     region_of_interest
+    exporting
     prototyping
     parametertree/index
     internals