Merge pull request #5443 from radarhere/fp

Author: hugovk

Tests/test_file_libtiff.py

@@ -578,6 +578,17 @@ def test_multipage_nframes(self):
 
         TiffImagePlugin.READ_LIBTIFF = False
 
+    def test_multipage_seek_backwards(self):
+        TiffImagePlugin.READ_LIBTIFF = True
+        with Image.open("Tests/images/multipage.tiff") as im:
+            im.seek(1)
+            im.load()
+
+            im.seek(0)
+            assert im.convert("RGB").getpixel((0, 0)) == (0, 128, 0)
+
+        TiffImagePlugin.READ_LIBTIFF = False
+
     def test__next(self):
         TiffImagePlugin.READ_LIBTIFF = True
         with Image.open("Tests/images/hopper.tif") as im:

src/PIL/TiffImagePlugin.py

@@ -1053,16 +1053,18 @@ def seek(self, frame):
 
     def _seek(self, frame):
         self.fp = self.__fp
+
+        # reset buffered io handle in case fp
+        # was passed to libtiff, invalidating the buffer
+        self.fp.tell()
+
         while len(self._frame_pos) <= frame:
             if not self.__next:
                 raise EOFError("no more images in TIFF file")
             logger.debug(
                 f"Seeking to frame {frame}, on frame {self.__frame}, "
                 f"__next {self.__next}, location: {self.fp.tell()}"
             )
-            # reset buffered io handle in case fp
-            # was passed to libtiff, invalidating the buffer
-            self.fp.tell()
             self.fp.seek(self.__next)
             self._frame_pos.append(self.__next)
             logger.debug("Loading tags, location: %s" % self.fp.tell())