check that PIL can save JPEG to BytesIO

as far as I can tell, this is a bug in PIL that is fixed in Pillow.

IPython/core/tests/test_pylabtools.py

@@ -1,224 +1,239 b''
 """Tests for pylab tools module.
 """
 #-----------------------------------------------------------------------------
 # Copyright (c) 2011, 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
 #-----------------------------------------------------------------------------
 from __future__ import print_function
 
+from io import UnsupportedOperation, BytesIO
+
 import matplotlib
 matplotlib.use('Agg')
 from matplotlib.figure import Figure
 
+from nose import SkipTest
 import nose.tools as nt
 
 from matplotlib import pyplot as plt
 import numpy as np
 
 # Our own imports
 from IPython.core.getipython import get_ipython
 from IPython.core.interactiveshell import InteractiveShell
 from IPython.core.display import _PNG, _JPEG
 from .. import pylabtools as pt
 
 from IPython.testing import decorators as dec
 
 #-----------------------------------------------------------------------------
 # Globals and constants
 #-----------------------------------------------------------------------------
 
 #-----------------------------------------------------------------------------
 # Local utilities
 #-----------------------------------------------------------------------------
 
 #-----------------------------------------------------------------------------
 # Classes and functions
 #-----------------------------------------------------------------------------
 
 def test_figure_to_svg():
     # simple empty-figure test
     fig = plt.figure()
     nt.assert_equal(pt.print_figure(fig, 'svg'), None)
 
     plt.close('all')
 
     # simple check for at least svg-looking output
     fig = plt.figure()
     ax = fig.add_subplot(1,1,1)
     ax.plot([1,2,3])
     plt.draw()
     svg = pt.print_figure(fig, 'svg')[:100].lower()
     nt.assert_in(b'doctype svg', svg)
 
+def _check_pil_jpeg_bytes():
+    """Skip if PIL can't write JPEGs to BytesIO objects"""
+    from PIL import Image
+    buf = BytesIO()
+    img = Image.new("RGB", (4,4))
+    try:
+        img.save(buf, 'jpeg')
+    except Exception as e:
+        ename = e.__class__.__name__
+        raise SkipTest("PIL can't write JPEG to BytesIO: %s: %s" % (ename, e))
+
 @dec.skip_without("PIL.Image")
-def test_figure_to_jpg():
-    # simple check for at least jpg-looking output
+def test_figure_to_jpeg():
+    _check_pil_jpeg_bytes()
+    # simple check for at least jpeg-looking output
     fig = plt.figure()
     ax = fig.add_subplot(1,1,1)
     ax.plot([1,2,3])
     plt.draw()
-    jpg = pt.print_figure(fig, 'jpg', quality=50)[:100].lower()
-    assert jpg.startswith(_JPEG)
+    jpeg = pt.print_figure(fig, 'jpeg', quality=50)[:100].lower()
+    assert jpeg.startswith(_JPEG)
 
 def test_retina_figure():
     fig = plt.figure()
     ax = fig.add_subplot(1,1,1)
     ax.plot([1,2,3])
     plt.draw()
     png, md = pt.retina_figure(fig)
     assert png.startswith(_PNG)
     nt.assert_in('width', md)
     nt.assert_in('height', md)
 
 _fmt_mime_map = {
     'png': 'image/png',
     'jpeg': 'image/jpeg',
     'pdf': 'application/pdf',
     'retina': 'image/png',
     'svg': 'image/svg+xml',
 }
 
 def test_select_figure_formats_str():
     ip = get_ipython()
     for fmt, active_mime in _fmt_mime_map.items():
         pt.select_figure_formats(ip, fmt)
         for mime, f in ip.display_formatter.formatters.items():
             if mime == active_mime:
                 nt.assert_in(Figure, f)
             else:
                 nt.assert_not_in(Figure, f)
 
 def test_select_figure_formats_kwargs():
     ip = get_ipython()
     kwargs = dict(quality=10, bbox_inches='tight')
     pt.select_figure_formats(ip, 'png', **kwargs)
     formatter = ip.display_formatter.formatters['image/png']
     f = formatter.lookup_by_type(Figure)
     cell = f.__closure__[0].cell_contents
     nt.assert_equal(cell, kwargs)
     
     # check that the formatter doesn't raise
     fig = plt.figure()
     ax = fig.add_subplot(1,1,1)
     ax.plot([1,2,3])
     plt.draw()
     formatter.enabled = True
     png = formatter(fig)
     assert png.startswith(_PNG)
 
 def test_select_figure_formats_set():
     ip = get_ipython()
     for fmts in [
         {'png', 'svg'},
         ['png'],
         ('jpeg', 'pdf', 'retina'),
         {'svg'},
     ]:
         active_mimes = {_fmt_mime_map[fmt] for fmt in fmts}
         pt.select_figure_formats(ip, fmts)
         for mime, f in ip.display_formatter.formatters.items():
             if mime in active_mimes:
                 nt.assert_in(Figure, f)
             else:
                 nt.assert_not_in(Figure, f)
 
 def test_select_figure_formats_bad():
     ip = get_ipython()
     with nt.assert_raises(ValueError):
         pt.select_figure_formats(ip, 'foo')
     with nt.assert_raises(ValueError):
         pt.select_figure_formats(ip, {'png', 'foo'})
     with nt.assert_raises(ValueError):
         pt.select_figure_formats(ip, ['retina', 'pdf', 'bar', 'bad'])
 
 def test_import_pylab():
     ns = {}
     pt.import_pylab(ns, import_all=False)
     nt.assert_true('plt' in ns)
     nt.assert_equal(ns['np'], np)
 
 class TestPylabSwitch(object):
     class Shell(InteractiveShell):
         def enable_gui(self, gui):
             pass
     
     def setup(self):
         import matplotlib
         def act_mpl(backend):
             matplotlib.rcParams['backend'] = backend
 
         # Save rcParams since they get modified
         self._saved_rcParams = matplotlib.rcParams
         self._saved_rcParamsOrig = matplotlib.rcParamsOrig
         matplotlib.rcParams = dict(backend='Qt4Agg')
         matplotlib.rcParamsOrig = dict(backend='Qt4Agg')
 
         # Mock out functions
         self._save_am = pt.activate_matplotlib
         pt.activate_matplotlib = act_mpl
         self._save_ip = pt.import_pylab
         pt.import_pylab = lambda *a,**kw:None
         self._save_cis = pt.configure_inline_support
         pt.configure_inline_support = lambda *a,**kw:None
 
     def teardown(self):
         pt.activate_matplotlib = self._save_am
         pt.import_pylab = self._save_ip
         pt.configure_inline_support = self._save_cis
         import matplotlib
         matplotlib.rcParams = self._saved_rcParams
         matplotlib.rcParamsOrig = self._saved_rcParamsOrig
 
     def test_qt(self):
         s = self.Shell()
         gui, backend = s.enable_matplotlib(None)
         nt.assert_equal(gui, 'qt')
         nt.assert_equal(s.pylab_gui_select, 'qt')
 
         gui, backend = s.enable_matplotlib('inline')
         nt.assert_equal(gui, 'inline')
         nt.assert_equal(s.pylab_gui_select, 'qt')
 
         gui, backend = s.enable_matplotlib('qt')
         nt.assert_equal(gui, 'qt')
         nt.assert_equal(s.pylab_gui_select, 'qt')
 
         gui, backend = s.enable_matplotlib('inline')
         nt.assert_equal(gui, 'inline')
         nt.assert_equal(s.pylab_gui_select, 'qt')
 
         gui, backend = s.enable_matplotlib()
         nt.assert_equal(gui, 'qt')
         nt.assert_equal(s.pylab_gui_select, 'qt')
 
     def test_inline(self):
         s = self.Shell()
         gui, backend = s.enable_matplotlib('inline')
         nt.assert_equal(gui, 'inline')
         nt.assert_equal(s.pylab_gui_select, None)
 
         gui, backend = s.enable_matplotlib('inline')
         nt.assert_equal(gui, 'inline')
         nt.assert_equal(s.pylab_gui_select, None)
 
         gui, backend = s.enable_matplotlib('qt')
         nt.assert_equal(gui, 'qt')
         nt.assert_equal(s.pylab_gui_select, 'qt')
 
     def test_qt_gtk(self):
         s = self.Shell()
         gui, backend = s.enable_matplotlib('qt')
         nt.assert_equal(gui, 'qt')
         nt.assert_equal(s.pylab_gui_select, 'qt')
 
         gui, backend = s.enable_matplotlib('gtk')
         nt.assert_equal(gui, 'qt')
         nt.assert_equal(s.pylab_gui_select, 'qt')