Handle truncated chunks at the end of PNG images

Tests/test_file_png.py

@@ -778,6 +778,18 @@ class MyStdOut:
         with Image.open(mystdout) as reloaded:
             assert_image_equal_tofile(reloaded, TEST_PNG_FILE)
 
+    def test_truncated_end_chunk(self):
+        with Image.open("Tests/images/truncated_end_chunk.png") as im:
+            with pytest.raises(OSError):
+                im.load()
+
+        ImageFile.LOAD_TRUNCATED_IMAGES = True
+        try:
+            with Image.open("Tests/images/truncated_end_chunk.png") as im:
+                assert_image_equal_tofile(im, "Tests/images/hopper.png")
+        finally:
+            ImageFile.LOAD_TRUNCATED_IMAGES = False
+
 
 @pytest.mark.skipif(is_win32(), reason="Requires Unix or macOS")
 @skip_unless_feature("zlib")

src/PIL/PngImagePlugin.py

@@ -981,7 +981,13 @@
             except EOFError:
                 if cid == b"fdAT":
                     length -= 4
-                ImageFile._safe_read(self.fp, length)
+                try:
+                    ImageFile._safe_read(self.fp, length)
+                except OSError as e:
+                    if ImageFile.LOAD_TRUNCATED_IMAGES:
+                        break
+                    else:
+                        raise e
             except AttributeError:
                 logger.debug("%r %s %s (unknown)", cid, pos, length)
                 s = ImageFile._safe_read(self.fp, length)