PSD layer co-ordinates may be negative

Tests/test_file_psd.py

@@ -113,6 +113,11 @@ def test_rgba() -> None:
         assert_image_equal_tofile(im, "Tests/images/imagedraw_square.png")
 
 
+def test_negative_top_left_layer() -> None:
+    with Image.open("Tests/images/negative_top_left_layer.psd") as im:
+        assert im.layers[0][2] == (-50, -50, 50, 50)
+
+
 def test_layer_skip() -> None:
     with Image.open("Tests/images/five_channels.psd") as im:
         assert im.n_frames == 1

src/PIL/PsdImagePlugin.py

@@ -24,6 +24,7 @@
 from ._binary import i16be as i16
 from ._binary import i32be as i32
 from ._binary import si16be as si16
+from ._binary import si32be as si32
 
 MODES = {
     # (photoshop mode, bits) -> (pil mode, required channels)
@@ -177,22 +178,21 @@ def read(size):
 
     for _ in range(abs(ct)):
         # bounding box
-        y0 = i32(read(4))
-        x0 = i32(read(4))
-        y1 = i32(read(4))
-        x1 = i32(read(4))
+        y0 = si32(read(4))
+        x0 = si32(read(4))
+        y1 = si32(read(4))
+        x1 = si32(read(4))
 
         # image info
         mode = []
         ct_types = i16(read(2))
-        types = list(range(ct_types))
-        if len(types) > 4:
-            fp.seek(len(types) * 6 + 12, io.SEEK_CUR)
+        if ct_types > 4:
+            fp.seek(ct_types * 6 + 12, io.SEEK_CUR)
             size = i32(read(4))
             fp.seek(size, io.SEEK_CUR)
             continue
 
-        for _ in types:
+        for _ in range(ct_types):
             type = i16(read(2))
 
             if type == 65535:

src/PIL/_binary.py

@@ -77,6 +77,16 @@ def si32le(c: bytes, o: int = 0) -> int:
     return unpack_from("<i", c, o)[0]
 
 
+def si32be(c: bytes, o: int = 0) -> int:
+    """
+    Converts a 4-bytes (32 bits) string to a signed integer, big endian.
+
+    :param c: string containing bytes to convert
+    :param o: offset of bytes to convert in string
+    """
+    return unpack_from(">i", c, o)[0]
+
+
 def i16be(c: bytes, o: int = 0) -> int:
     return unpack_from(">H", c, o)[0]