Deprecate support for libtiff < 4

docs/deprecations.rst

@@ -100,6 +100,14 @@ ImageMath eval()
 ``ImageMath.eval()`` has been deprecated. Use :py:meth:`~PIL.ImageMath.lambda_eval` or
 :py:meth:`~PIL.ImageMath.unsafe_eval` instead.
 
+Support for LibTIFF earlier than 4
+^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+
+.. deprecated:: 10.4.0
+
+Support for LibTIFF earlier than version 4 has been deprecated.
+Upgrade to a newer version of LibTIFF instead.
+
 Removed features
 ----------------
 

docs/releasenotes/10.4.0.rst

@@ -0,0 +1,54 @@
+10.4.0
+------
+
+Security
+========
+
+TODO
+^^^^
+
+TODO
+
+:cve:`YYYY-XXXXX`: TODO
+^^^^^^^^^^^^^^^^^^^^^^^
+
+TODO
+
+Backwards Incompatible Changes
+==============================
+
+TODO
+^^^^
+
+Deprecations
+============
+
+Support for LibTIFF earlier than 4
+^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+
+Support for LibTIFF earlier than version 4 has been deprecated.
+Upgrade to a newer version of LibTIFF instead.
+
+API Changes
+===========
+
+TODO
+^^^^
+
+TODO
+
+API Additions
+=============
+
+TODO
+^^^^
+
+TODO
+
+Other Changes
+=============
+
+TODO
+^^^^
+
+TODO

docs/releasenotes/index.rst

@@ -14,6 +14,7 @@ expected to be backported to earlier versions.
 .. toctree::
   :maxdepth: 2
 
+  10.4.0
   10.3.0
   10.2.0
   10.1.0

src/PIL/TiffImagePlugin.py

@@ -56,6 +56,7 @@
 from ._binary import i16be as i16
 from ._binary import i32be as i32
 from ._binary import o8
+from ._deprecate import deprecate
 from .TiffTags import TYPES
 
 logger = logging.getLogger(__name__)
@@ -276,6 +277,9 @@
     b"II\x2B\x00",  # BigTIFF with little-endian byte order
 ]
 
+if not getattr(Image.core, "libtiff_support_custom_tags", True):
+    deprecate("Support for LibTIFF earlier than version 4", 12)
+
 
 def _accept(prefix: bytes) -> bool:
     return prefix[:4] in PREFIXES