Minor refactoring per discussion and MPO docs.

PIL/Image.py

@@ -2236,19 +2236,6 @@ def open(fp, mode="r"):
                 fp.seek(0)
                 im = factory(fp, filename)
                 _decompression_bomb_check(im.size)
-                if i == 'JPEG':
-                    # Things are more complicated for JPEGs; we need to parse
-                    # more deeply than 16 characters and check the contents of
-                    # a potential MP header block to be sure.
-                    mpheader = im._getmp()
-                    try:
-                        if mpheader[45057] > 1:
-                            # It's actually an MPO
-                            factory, accept = OPEN['MPO']
-                            im = factory(fp, filename)
-                    except (TypeError, IndexError):
-                        # It is really a JPEG
-                        pass
                 return im
         except (SyntaxError, IndexError, TypeError):
             # import traceback

PIL/JpegImagePlugin.py

@@ -663,10 +663,27 @@ def _save_cjpeg(im, fp, filename):
     except:
         pass
 
+
+##
+# Factory for making JPEG and MPO instances
+def jpeg_factory(fp=None, filename=None):
+    im = JpegImageFile(fp, filename)
+    mpheader = im._getmp()
+    try:
+        if mpheader[45057] > 1:
+            # It's actually an MPO
+            from MpoImagePlugin import MpoImageFile
+            im = MpoImageFile(fp, filename)
+    except (TypeError, IndexError):
+        # It is really a JPEG
+        pass
+    return im
+
+
 # -------------------------------------------------------------------q-
 # Registry stuff
 
-Image.register_open("JPEG", JpegImageFile, _accept)
+Image.register_open("JPEG", jpeg_factory, _accept)
 Image.register_save("JPEG", _save)
 
 Image.register_extension("JPEG", ".jfif")

PIL/MpoImagePlugin.py

@@ -37,6 +37,7 @@ class MpoImageFile(JpegImagePlugin.JpegImageFile):
     format_description = "MPO (CIPA DC-007)"
 
     def _open(self):
+        self.fp.seek(0) # prep the fp in order to pass the JPEG test
         JpegImagePlugin.JpegImageFile._open(self)
         self.mpinfo = self._getmp()
         self.__framecount = self.mpinfo[0xB001]
@@ -73,7 +74,7 @@ class MpoImageFile(JpegImagePlugin.JpegImageFile):
 # -------------------------------------------------------------------q-
 # Registry stuff
 
-Image.register_open("MPO", MpoImageFile, _accept)
+Image.register_open("MPO", JpegImagePlugin.jpeg_factory, _accept)
 Image.register_save("MPO", _save)
 
 Image.register_extension("MPO", ".mpo")

docs/handbook/image-file-formats.rst

@@ -588,6 +588,20 @@ PIL identifies and reads Microsoft Image Composer (MIC) files. When opened, the
 first sprite in the file is loaded. You can use :py:meth:`~file.seek` and
 :py:meth:`~file.tell` to read other sprites from the file.
 
+MPO
+^^^
+
+PIL identifies and reads Multi Picture Object (MPO) files, loading the primary
+image when first opened. The :py:meth:`~file.seek` and :py:meth:`~file.tell`
+methods may be used to read other pictures from the file. The pictures are
+zero-indexed and random access is supported.
+
+MIC (read only)
+
+PIL identifies and reads Microsoft Image Composer (MIC) files. When opened, the
+first sprite in the file is loaded. You can use :py:meth:`~file.seek` and
+:py:meth:`~file.tell` to read other sprites from the file.
+
 PCD
 ^^^