Added reading of JPEG2000 comments

Tests/test_file_jpeg2k.py

@@ -354,6 +354,11 @@ def test_subsampling_decode(name):
         assert_image_similar(im, expected, epsilon)
 
 
+def test_comment():
+    with Image.open("Tests/images/comment.jp2") as im:
+        assert im.info["comment"] == b"Created by OpenJPEG version 2.5.0"
+
+
 @pytest.mark.parametrize(
     "test_file",
     [

src/PIL/Jpeg2KImagePlugin.py

@@ -218,6 +218,8 @@ def _open(self):
                 self._size, self.mode, self.custom_mimetype, dpi = header
                 if dpi is not None:
                     self.info["dpi"] = dpi
+                if self.fp.read(12).endswith(b"jp2c\xff\x4f\xff\x51"):
+                    self._parse_comment()
             else:
                 msg = "not a JPEG 2000 file"
                 raise SyntaxError(msg)
@@ -254,6 +256,27 @@ def _open(self):
             )
         ]
 
+    def _parse_comment(self):
+        hdr = self.fp.read(2)
+        lsiz = struct.unpack(">H", hdr)[0]
+        siz = hdr + self.fp.read(lsiz - 2)
+
+        while True:
+            marker = self.fp.read(2)
+            if not marker:
+                break
+            typ = marker[1]
+            if typ in (0x90, 0xD9):
+                # Start of tile or end of codestream
+                break
+            hdr = self.fp.read(2)
+            length = struct.unpack(">H", hdr)[0]
+            data = hdr + self.fp.read(length - 2)
+            if typ == 0x64:
+                # Comment
+                self.info["comment"] = data[4:]
+                break
+
     @property
     def reduce(self):
         # https://github.com/python-pillow/Pillow/issues/4343 found that the