fix b64-handling of data in Python 3

IPython/nbconvert/transformers/extractfigure.py

@@ -1,99 +1,96 b''
 """Module containing a transformer that extracts all of the figures from the
 notebook file.  The extracted figures are returned in the 'resources' dictionary.
 """
 #-----------------------------------------------------------------------------
 # Copyright (c) 2013, the IPython Development Team.
 #
 # Distributed under the terms of the Modified BSD License.
 #
 # The full license is in the file COPYING.txt, distributed with this software.
 #-----------------------------------------------------------------------------
 
 #-----------------------------------------------------------------------------
 # Imports
 #-----------------------------------------------------------------------------
 
+import base64
 import sys
+
 from IPython.utils.traitlets import Unicode
 from .base import Transformer
 from IPython.utils import py3compat
 
 #-----------------------------------------------------------------------------
 # Classes
 #-----------------------------------------------------------------------------
 
 class ExtractFigureTransformer(Transformer):
     """
     Extracts all of the figures from the notebook file.  The extracted 
     figures are returned in the 'resources' dictionary.
     """
 
     figure_filename_template = Unicode(
         "{unique_key}_{cell_index}_{index}.{extension}", config=True)
 
 
     def transform_cell(self, cell, resources, cell_index):
         """
         Apply a transformation on each cell,
         
         Parameters
         ----------
         cell : NotebookNode cell
             Notebook cell being processed
         resources : dictionary
             Additional resources used in the conversion process.  Allows
             transformers to pass variables into the Jinja engine.
         cell_index : int
             Index of the cell being processed (see base.py)
         """
 
         #Get the unique key from the resource dict if it exists.  If it does not 
         #exist, use 'figure' as the default.
         unique_key = resources.get('unique_key', 'figure')
         
         #Make sure figures key exists
         if not 'figures' in resources:
             resources['figures'] = {}
             
         #Loop through all of the outputs in the cell
         for index, out in enumerate(cell.get('outputs', [])):
 
             #Get the output in data formats that the template is interested in.
             for out_type in self.display_data_priority:
                 if out.hasattr(out_type):
                     data = out[out_type]
 
                     #Binary files are base64-encoded, SVG is already XML
                     if out_type in ('png', 'jpg', 'jpeg', 'pdf'):
-                        
-                        #Python3 base64 is in a separate library...
-                        if py3compat.PY3:
-                            
-                            #Base 64 decode the bytes
-                            import base64
-                            data = base64.b64decode(data)
-                        else:
-                            data = data.decode('base64')
+                        # data is b64-encoded as text (str, unicode)
+                        # decodestring only accepts bytes
+                        data = py3compat.cast_bytes(data)
+                        data = base64.decodestring(data)
                     elif sys.platform == 'win32':
                         data = data.replace('\n', '\r\n').encode("UTF-8")
                     else:
                         data = data.encode("UTF-8")
                     
                     #Build a figure name
                     figure_name = self.figure_filename_template.format( 
                                     unique_key=unique_key,
                                     cell_index=cell_index,
                                     index=index,
                                     extension=out_type)
 
                     #On the cell, make the figure available via 
                     #   cell.outputs[i].svg_filename  ... etc (svg in example)
                     # Where
                     #   cell.outputs[i].svg  contains the data
                     out[out_type + '_filename'] = figure_name
 
                     #In the resources, make the figure available via
                     #   resources['figures']['filename'] = data
                     resources['figures'][figure_name] = data
 
         return cell, resources