Read textual chunks located after IDAT chunks

Tests/test_file_png.py

@@ -557,6 +557,28 @@ class TestFilePng(PillowTestCase):
         chunks = PngImagePlugin.getchunks(im)
         self.assertEqual(len(chunks), 3)
 
+    def test_textual_chunks_after_idat(self):
+        im = Image.open("Tests/images/hopper.png")
+        self.assertIn('comment', im.text.keys())
+        for k, v in {
+            'date:create': '2014-09-04T09:37:08+03:00',
+            'date:modify': '2014-09-04T09:37:08+03:00',
+        }.items():
+            self.assertEqual(im.text[k], v)
+
+        # Raises a SyntaxError in load_end
+        im = Image.open("Tests/images/broken_data_stream.png")
+        with self.assertRaises(IOError):
+            self.assertIsInstance(im.text, dict)
+
+        # Raises a UnicodeDecodeError in load_end
+        im = Image.open("Tests/images/truncated_image.png")
+        # The file is truncated
+        self.assertRaises(IOError, lambda: im.text)
+        ImageFile.LOAD_TRUNCATED_IMAGES = True
+        self.assertIsInstance(im.text, dict)
+        ImageFile.LOAD_TRUNCATED_IMAGES = False
+
 
 @unittest.skipIf(sys.platform.startswith('win32'), "requires Unix or macOS")
 class TestTruncatedPngPLeaks(PillowLeakTestCase):

src/PIL/PngImagePlugin.py

@@ -579,7 +579,7 @@ class PngImageFile(ImageFile.ImageFile):
         self.mode = self.png.im_mode
         self._size = self.png.im_size
         self.info = self.png.im_info
-        self.text = self.png.im_text  # experimental
+        self._text = None
         self.tile = self.png.im_tile
 
         if self.png.im_palette:
@@ -588,6 +588,15 @@ class PngImageFile(ImageFile.ImageFile):
 
         self.__idat = length  # used by load_read()
 
+    @property
+    def text(self):
+        # experimental
+        if self._text is None:
+            # iTxt, tEXt and zTXt chunks may appear at the end of the file
+            # So load the file to ensure that they are read
+            self.load()
+        return self._text
+
     def verify(self):
         "Verify PNG file"
 
@@ -640,7 +649,22 @@ class PngImageFile(ImageFile.ImageFile):
 
     def load_end(self):
         "internal: finished reading image data"
+        while True:
+            self.fp.read(4)  # CRC
 
+            try:
+                cid, pos, length = self.png.read()
+            except (struct.error, SyntaxError):
+                break
+
+            if cid == b"IEND":
+                break
+
+            try:
+                self.png.call(cid, pos, length)
+            except UnicodeDecodeError:
+                break
+        self._text = self.png.im_text
         self.png.close()
         self.png = None