Do not read layers when opening

Tests/test_file_psd.py

@@ -4,7 +4,7 @@ import warnings
 
 import pytest
 
-from PIL import Image, PsdImagePlugin, UnidentifiedImageError
+from PIL import Image, PsdImagePlugin
 
 from .helper import assert_image_equal_tofile, assert_image_similar, hopper, is_pypy
 
@@ -150,14 +150,6 @@ def test_combined_larger_than_size() -> None:
 @pytest.mark.parametrize(
     "test_file,raises",
     [
-        (
-            "Tests/images/timeout-1ee28a249896e05b83840ae8140622de8e648ba9.psd",
-            UnidentifiedImageError,
-        ),
-        (
-            "Tests/images/timeout-598843abc37fc080ec36a2699ebbd44f795d3a6f.psd",
-            UnidentifiedImageError,
-        ),
         ("Tests/images/timeout-c8efc3fded6426986ba867a399791bae544f59bc.psd", OSError),
         ("Tests/images/timeout-dedc7a4ebd856d79b4359bbcc79e8ef231ce38f6.psd", OSError),
     ],
@@ -167,3 +159,17 @@ def test_crashes(test_file: str, raises) -> None:
         with pytest.raises(raises):
             with Image.open(f):
                 pass
+
+
+@pytest.mark.parametrize(
+    "test_file",
+    [
+        "Tests/images/timeout-1ee28a249896e05b83840ae8140622de8e648ba9.psd",
+        "Tests/images/timeout-598843abc37fc080ec36a2699ebbd44f795d3a6f.psd",
+    ],
+)
+def test_layer_crashes(test_file: str) -> None:
+    with open(test_file, "rb") as f:
+        with Image.open(f) as im:
+            with pytest.raises(SyntaxError):
+                im.layers

src/PIL/PsdImagePlugin.py

@@ -18,6 +18,7 @@
 from __future__ import annotations
 
 import io
+from functools import cached_property
 
 from . import Image, ImageFile, ImagePalette
 from ._binary import i8
@@ -118,18 +119,17 @@ class PsdImageFile(ImageFile.ImageFile):
         #
         # layer and mask information
 
-        self.layers = []
+        self._layers_position = None
 
         size = i32(read(4))
         if size:
             end = self.fp.tell() + size
             size = i32(read(4))
             if size:
-                _layer_data = io.BytesIO(ImageFile._safe_read(self.fp, size))
-                self.layers = _layerinfo(_layer_data, size)
+                self._layers_position = self.fp.tell()
+                self._layers_size = size
             self.fp.seek(end)
-        self.n_frames = len(self.layers)
-        self.is_animated = self.n_frames > 1
+        self._n_frames: int | None = None
 
         #
         # image descriptor
@@ -141,6 +141,26 @@ class PsdImageFile(ImageFile.ImageFile):
         self.frame = 1
         self._min_frame = 1
 
+    @cached_property
+    def layers(self):
+        layers = []
+        if self._layers_position is not None:
+            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)
+        self._n_frames = len(layers)
+        return layers
+
+    @property
+    def n_frames(self) -> int:
+        if self._n_frames is None:
+            self._n_frames = len(self.layers)
+        return self._n_frames
+
+    @property
+    def is_animated(self) -> bool:
+        return len(self.layers) > 1
+
     def seek(self, layer: int) -> None:
         if not self._seek_check(layer):
             return