Added support for custom commands for show

Previously the command option to show had no effect, now, if it is set it will
use that command to show the image.

We still need to add some checks to the code.

PIL/ImageShow.py

@@ -35,15 +35,25 @@ def register(viewer, order=1):
 #
 # @param image An image object.
 # @param title Optional title.  Not all viewers can display the title.
+# @param command Optional command. Command to display the image with.
 # @param **options Additional viewer options.
 # @return True if a suitable viewer was found, false otherwise.
 
-def show(image, title=None, **options):
+def show(image, title=None, command=None, **options):
+    if command is not None:
+        return _showWithCommand(image,command,title=title,**options)
     for viewer in _viewers:
         if viewer.show(image, title=title, **options):
             return 1
     return 0
 
+def _showWithCommand(image,command,**options):
+    viewer = CustomCommandViewer(command)
+    #TODO: Should we register these viewers and see if there is already a
+    #viewer for this command?
+    viewer.show(image,**options)
+    return True
+
 ##
 # Base class for viewers.
 
@@ -140,6 +150,16 @@ else:
 
     # implementations
 
+    class CustomCommandViewer(UnixViewer):
+
+        def __init__(self,command):
+            super(CustomCommandViewer, self).__init__()
+            self._command = command
+
+        def get_command_ex(self, file, **options):
+            command = executable = self._command
+            return command, executable
+
     class DisplayViewer(UnixViewer):
         def get_command_ex(self, file, **options):
             command = executable = "display"