Only read different sizes for "Large Thumbnail" frames

Tests/test_file_mpo.py

@@ -89,6 +89,17 @@ def test_frame_size():
         assert im.size == (680, 480)
 
 
+def test_ignore_frame_size():
+    # Ignore the different size of the second frame
+    # since this is not a "Large Thumbnail" image
+    with Image.open("Tests/images/ignore_frame_size.mpo") as im:
+        assert im.size == (64, 64)
+
+        im.seek(1)
+        assert im.mpinfo[0xB002][1]['Attribute']['MPType'] == "Multi-Frame Image: (Disparity)"
+        assert im.size == (64, 64)
+
+
 def test_parallax():
     # Nintendo
     with Image.open("Tests/images/sugarshack.mpo") as im:
@@ -132,7 +143,7 @@ def test_mp_attribute():
         with Image.open(test_file) as im:
             mpinfo = im._getmp()
         frameNumber = 0
-        for mpentry in mpinfo[45058]:
+        for mpentry in mpinfo[0xB002]:
             mpattr = mpentry["Attribute"]
             if frameNumber:
                 assert not mpattr["RepresentativeImageFlag"]

src/PIL/MpoImagePlugin.py

@@ -82,9 +82,11 @@ class MpoImageFile(JpegImagePlugin.JpegImageFile):
             n = i16(self.fp.read(2)) - 2
             self.info["exif"] = ImageFile._safe_read(self.fp, n)
 
-            exif = self.getexif()
-            if 40962 in exif and 40963 in exif:
-                self._size = (exif[40962], exif[40963])
+            mptype = self.mpinfo[0xB002][frame]["Attribute"]["MPType"]
+            if mptype.startswith("Large Thumbnail"):
+                exif = self.getexif()
+                if 40962 in exif and 40963 in exif:
+                    self._size = (exif[40962], exif[40963])
         elif "exif" in self.info:
             del self.info["exif"]