Add image message handler in ZMQTerminalInteractiveShell

This change introduces handler for messages which contain image in
ZMQTerminalInteractiveShell.  This is useful, for example, when
connecting to the kernel in which pylab inline backend is activated.
Current image handler only supports PIL backend.

IPython/frontend/terminal/console/interactiveshell.py

@@ -21,13 +21,21 b' import bdb'
 import signal
 import sys
 import time
+from cStringIO import StringIO
+import base64
 
 from Queue import Empty
 
+try:
+    import PIL
+except ImportError:
+    PIL = None
+
 from IPython.core.alias import AliasManager, AliasError
 from IPython.core import page
 from IPython.utils.warn import warn, error, fatal
 from IPython.utils import io
+from IPython.utils.traitlets import List
 
 from IPython.frontend.terminal.interactiveshell import TerminalInteractiveShell
 from IPython.frontend.terminal.console.completer import ZMQCompleter
@@ -36,7 +44,18 b' from IPython.frontend.terminal.console.completer import ZMQCompleter'
 class ZMQTerminalInteractiveShell(TerminalInteractiveShell):
     """A subclass of TerminalInteractiveShell that uses the 0MQ kernel"""
     _executing = False
-    
+
+    image_handler = List([], allow_none=False, config=True, help=
+        """
+        Handlers for image type output.  This is useful, for example,
+        when connecting to the kernel in which pylab inline backend is
+        activated.  Handlers in the list is tried one-by-one and first
+        available handler is used.  Currently IPython only supports
+        handler `PIL`.  IPython shell pops up window to show image
+        when the kernel sends image (e.g., when you plot a graph).
+        """
+    )
+
     def __init__(self, *args, **kwargs):
         self.km = kwargs.pop('kernel_manager')
         self.session_id = self.km.session.session
@@ -163,6 +182,7 b' class ZMQTerminalInteractiveShell(TerminalInteractiveShell):'
                 elif msg_type == 'pyout':
                     self.execution_count = int(sub_msg["content"]["execution_count"])
                     format_dict = sub_msg["content"]["data"]
+                    self.handle_rich_data(format_dict)
                     # taken from DisplayHook.__call__:
                     hook = self.displayhook
                     hook.start_displayhook()
@@ -171,6 +191,21 b' class ZMQTerminalInteractiveShell(TerminalInteractiveShell):'
                     hook.log_output(format_dict)
                     hook.finish_displayhook()
 
+                elif msg_type == 'display_data':
+                    self.handle_rich_data(sub_msg["content"]["data"])
+
+    def handle_rich_data(self, data):
+        if 'image/png' in data:
+            self.handle_image(data['image/png'])
+        elif 'image/jpeg' in data:
+            self.handle_image(data['image/jpeg'])
+
+    def handle_image(self, string):
+        if 'PIL' in self.image_handler and PIL:
+            data = base64.decodestring(string)
+            img = PIL.Image.open(StringIO(data))
+            img.show()
+
     def handle_stdin_request(self, timeout=0.1):
         """ Method to capture raw_input
         """