Fix PSD layer tiles reading from the wrong file offset

Tests/test_file_psd.py

@@ -9,6 +9,7 @@
 from PIL import Image, PsdImagePlugin
 
 from .helper import (
+    assert_image_equal,
     assert_image_equal_tofile,
     assert_image_similar,
     hopper,
@@ -111,6 +112,17 @@ def test_seek_tell() -> None:
     assert layer_number == 2
 
 
+def test_seek_back_to_initial_frame() -> None:
+    # Seeking away from the initial frame and then back should produce the same image
+    with Image.open(test_file) as im:
+        initial_frame = im.copy()
+
+        im.seek(2)
+        im.seek(1)
+
+        assert_image_equal(im, initial_frame)
+
+
 def test_seek_eoferror() -> None:
     with Image.open(test_file) as im:
         with pytest.raises(EOFError):
@@ -228,11 +240,5 @@ def test_bounds_crash_overflow() -> None:
     with Image.open("Tests/images/psd-oob-write-overflow.psd") as im:
         assert isinstance(im, PsdImagePlugin.PsdImageFile)
         im.load()
-        if sys.maxsize <= 2**32:
-            with pytest.raises(OverflowError):
-                im.seek(im.n_frames)
-        else:
+        with pytest.raises(OverflowError if sys.maxsize <= 2**32 else ValueError):
             im.seek(im.n_frames)
-
-            with pytest.raises(ValueError):
-                im.load()

docs/releasenotes/13.0.0.rst

@@ -228,3 +228,10 @@ position or contents.
 
 :py:meth:`~PIL.Image.Image.tobytes` also now explicitly cleans up its encoder on
 both success and failure, rather than relying on object destruction.
+
+Fixed reading PSD layers at the wrong file offset
+^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+
+When seeking to a layer of a PSD image, the pixel data was read from the wrong
+position in the file, so :py:meth:`~PIL.Image.Image.seek` returned unrelated
+bytes reinterpreted as image data instead of that layer's actual content.

src/PIL/PsdImagePlugin.py

@@ -158,8 +158,7 @@ def layers(
             if isinstance(self._fp, DeferredError):
                 raise self._fp.ex
             self._fp.seek(self._layers_position)
-            _layer_data = io.BytesIO(ImageFile._safe_read(self._fp, self._layers_size))
-            layers = _layerinfo(_layer_data, self._layers_size)
+            layers = _layerinfo(self._fp, self._layers_size)
         self._n_frames = len(layers)
         return layers