Test DIB header size

Tests/test_file_bmp.py

@@ -5,7 +5,7 @@
 
 import pytest
 
-from PIL import BmpImagePlugin, Image
+from PIL import _binary, BmpImagePlugin, Image
 
 from .helper import (
     assert_image_equal,
@@ -128,6 +128,29 @@ def test_load_dib() -> None:
         assert_image_equal_tofile(im, "Tests/images/clipboard_target.png")
 
 
+@pytest.mark.parametrize(
+    "header_size, path",
+    (
+        (12, "g/pal8os2.bmp"),
+        (40, "g/pal1.bmp"),
+        (52, "q/rgb32h52.bmp"),
+        (56, "q/rgba32h56.bmp"),
+        (64, "q/pal8os2v2.bmp"),
+        (108, "g/pal8v4.bmp"),
+        (124, "g/pal8v5.bmp"),
+    ),
+)
+def test_dib_header_size(header_size, path):
+    image_path = "Tests/images/bmp/" + path
+    with open(image_path, "rb") as fp:
+        data = fp.read()[14:]
+    assert _binary.i32le(data) == header_size
+
+    dib = io.BytesIO(data)
+    with Image.open(dib) as im:
+        im.load()
+
+
 def test_save_dib(tmp_path: Path) -> None:
     outfile = str(tmp_path / "temp.dib")