add InlineBackend.print_figure_kwargs

removes special handling of 'quality', in favor of passing arbitrary kwargs to fig.canvas.print_figure.

This lets people override the occasionally problematic use of `bbox_inches='tight'`,
and any potential future issue that might be solved by adding/changing kwargs to print_figure.

IPython/core/pylabtools.py

@@ -95,9 +95,11 b' def figsize(sizex, sizey):'
     matplotlib.rcParams['figure.figsize'] = [sizex, sizey]
 
 
-def print_figure(fig, fmt='png', quality=90):
-    """Convert a figure to svg, png or jpg for inline display.
-    Quality is only relevant for jpg.
+def print_figure(fig, fmt='png', **kwargs):
+    """Print a figure to an image, and return the resulting bytes
+    
+    Any extra keyword args are passed to fig.canvas.print_figure,
+    such as ``quality`` or ``bbox_inches``.
     """
     from matplotlib import rcParams
     # When there's an empty figure, we shouldn't return anything, otherwise we
@@ -105,21 +107,29 b" def print_figure(fig, fmt='png', quality=90):"
     if not fig.axes and not fig.lines:
         return
 
-    fc = fig.get_facecolor()
-    ec = fig.get_edgecolor()
-    bytes_io = BytesIO()
     dpi = rcParams['savefig.dpi']
     if fmt == 'retina':
         dpi = dpi * 2
         fmt = 'png'
-    fig.canvas.print_figure(bytes_io, format=fmt, bbox_inches='tight',
-                            facecolor=fc, edgecolor=ec, dpi=dpi, quality=quality)
-    data = bytes_io.getvalue()
-    return data
     
-def retina_figure(fig):
+    # build keyword args
+    kw = dict(
+        format=fmt,
+        fc=fig.get_facecolor(),
+        ec=fig.get_edgecolor(),
+        dpi=dpi,
+    )
+    # **kwargs get higher priority
+    kw.update(kwargs)
+    print(kw)
+    
+    bytes_io = BytesIO()
+    fig.canvas.print_figure(bytes_io, **kw)
+    return bytes_io.getvalue()
+    
+def retina_figure(fig, **kwargs):
     """format a figure as a pixel-doubled (retina) PNG"""
-    pngdata = print_figure(fig, fmt='retina')
+    pngdata = print_figure(fig, fmt='retina', **kwargs)
     w, h = _pngxy(pngdata)
     metadata = dict(width=w//2, height=h//2)
     return pngdata, metadata
@@ -166,17 +176,17 b' def mpl_runner(safe_execfile):'
     return mpl_execfile
 
 
-def select_figure_formats(shell, formats, quality=90):
+def select_figure_formats(shell, formats, **kwargs):
     """Select figure formats for the inline backend.
 
     Parameters
     ==========
     shell : InteractiveShell
         The main IPython instance.
-    formats : list
+    formats : str or set
         One or a set of figure formats to enable: 'png', 'retina', 'jpeg', 'svg', 'pdf'.
-    quality : int
-        A percentage for the quality of JPEG figures.
+    **kwargs : any
+        Extra keyword arguments to be passed to fig.canvas.print_figure.
     """
     from matplotlib.figure import Figure
     from IPython.kernel.zmq.pylab import backend_inline
@@ -188,22 +198,27 b' def select_figure_formats(shell, formats, quality=90):'
 
     if isinstance(formats, py3compat.string_types):
         formats = {formats}
-
-    [ f.type_printers.pop(Figure, None) for f in {svg_formatter, png_formatter, jpg_formatter} ]
-
-    for fmt in formats:
-        if fmt == 'png':
-            png_formatter.for_type(Figure, lambda fig: print_figure(fig, 'png'))
-        elif fmt in ('png2x', 'retina'):
-            png_formatter.for_type(Figure, retina_figure)
-        elif fmt in ('jpg', 'jpeg'):
-            jpg_formatter.for_type(Figure, lambda fig: print_figure(fig, 'jpg', quality))
-        elif fmt == 'svg':
-            svg_formatter.for_type(Figure, lambda fig: print_figure(fig, 'svg'))
-        elif fmt == 'pdf':
-            pdf_formatter.for_type(Figure, lambda fig: print_figure(fig, 'pdf'))
-        else:
-            raise ValueError("supported formats are: 'png', 'retina', 'svg', 'jpg', 'pdf' not %r" % fmt)
+    # cast in case of list / tuple
+    formats = set(formats)
+
+    [ f.pop(Figure, None) for f in shell.display_formatter.formatters.values() ]
+    
+    supported = {'png', 'png2x', 'retina', 'jpg', 'jpeg', 'svg', 'pdf'}
+    bad = formats.difference(supported)
+    if bad:
+        s = "{%s}" % ",".join([repr(f) for f in bad])
+        raise ValueError("supported formats are: 'png', 'retina', 'svg', 'jpg', 'pdf' not %s" % s)
+    
+    if 'png' in formats:
+        png_formatter.for_type(Figure, lambda fig: print_figure(fig, 'png', **kwargs))
+    if 'retina' in formats or 'png2x' in formats:
+        png_formatter.for_type(Figure, lambda fig: retina_figure(fig, **kwargs))
+    if 'jpg' in formats or 'jpeg' in formats:
+        jpg_formatter.for_type(Figure, lambda fig: print_figure(fig, 'jpg', **kwargs))
+    if 'svg' in formats:
+        svg_formatter.for_type(Figure, lambda fig: print_figure(fig, 'svg', **kwargs))
+    if 'pdf' in formats:
+        pdf_formatter.for_type(Figure, lambda fig: print_figure(fig, 'pdf', **kwargs))
 
 #-----------------------------------------------------------------------------
 # Code for initializing matplotlib and importing pylab
@@ -354,5 +369,5 b' def configure_inline_support(shell, backend):'
             del shell._saved_rcParams
 
     # Setup the default figure format
-    select_figure_formats(shell, cfg.figure_formats, cfg.quality)
+    select_figure_formats(shell, cfg.figure_formats, **cfg.print_figure_kwargs)
 

IPython/kernel/zmq/pylab/config.py

@@ -69,6 +69,10 b' class InlineBackend(InlineBackendConfig):'
                           help="""A set of figure formats to enable: 'png', 
                           'retina', 'jpeg', 'svg', 'pdf'.""")
 
+    def _update_figure_formatters(self):
+        if self.shell is not None:
+            select_figure_formats(self.shell, self.figure_formats, **self.print_figure_kwargs)
+    
     def _figure_formats_changed(self, name, old, new):
         from IPython.core.pylabtools import select_figure_formats
         if 'jpg' in new or 'jpeg' in new:
@@ -77,7 +81,7 b' class InlineBackend(InlineBackendConfig):'
         if self.shell is None:
             return
         else:
-            select_figure_formats(self.shell, new)
+            self._update_figure_formatters()
 
     figure_format = Unicode(config=True, help="""The figure format to enable (deprecated
                                          use `figure_formats` instead)""")
@@ -86,12 +90,13 b' class InlineBackend(InlineBackendConfig):'
         if new:
             self.figure_formats = {new}
 
-    quality = Int(default_value=90, config=True,
-                  help="Quality of compression [10-100], currently for lossy JPEG only.")
+    print_figure_kwargs = Dict({'bbox_inches' : 'tight'}, config=True,
+        help="""Extra kwargs to be passed to fig.canvas.print_figure.
 
-    def _quality_changed(self, name, old, new):
-        if new < 10 or new > 100:
-            raise TraitError("figure JPEG quality must be in [10-100] range.")
+        Logical examples include: bbox_inches, quality (for jpeg figures), etc.
+        """
+    )
+    _print_figure_kwargs_changed = _update_figure_formatters
     
     close_figures = Bool(True, config=True,
         help="""Close all figures at the end of each cell.