Fixed saving EXIF data to MPO

Tests/test_file_mpo.py

@@ -80,7 +80,10 @@ def test_app(test_file):
 
 @pytest.mark.parametrize("test_file", test_files)
 def test_exif(test_file):
-    with Image.open(test_file) as im:
+    with Image.open(test_file) as im_original:
+        im_reloaded = roundtrip(im_original, save_all=True, exif=im_original.getexif())
+
+    for im in (im_original, im_reloaded):
         info = im._getexif()
         assert info[272] == "Nintendo 3DS"
         assert info[296] == 2

src/PIL/MpoImagePlugin.py

@@ -52,14 +52,22 @@ def _save_all(im, fp, filename):
             _save(im, fp, filename)
             return
 
+    mpf_offset = 28
     offsets = []
     for imSequence in itertools.chain([im], append_images):
         for im_frame in ImageSequence.Iterator(imSequence):
             if not offsets:
                 # APP2 marker
-                im.encoderinfo["extra"] = (
+                im_frame.encoderinfo["extra"] = (
                     b"\xFF\xE2" + struct.pack(">H", 6 + 82) + b"MPF\0" + b" " * 82
                 )
+                exif = im_frame.encoderinfo.get("exif")
+                if isinstance(exif, Image.Exif):
+                    exif = exif.tobytes()
+                    im_frame.encoderinfo["exif"] = exif
+                if exif:
+                    mpf_offset += 4 + len(exif)
+
                 JpegImagePlugin._save(im_frame, fp, filename)
                 offsets.append(fp.tell())
             else:
@@ -79,11 +87,11 @@ def _save_all(im, fp, filename):
             mptype = 0x000000  # Undefined
         mpentries += struct.pack("<LLLHH", mptype, size, data_offset, 0, 0)
         if i == 0:
-            data_offset -= 28
+            data_offset -= mpf_offset
         data_offset += size
     ifd[0xB002] = mpentries
 
-    fp.seek(28)
+    fp.seek(mpf_offset)
     fp.write(b"II\x2A\x00" + o32le(8) + ifd.tobytes(8))
     fp.seek(0, os.SEEK_END)