Remove undocumented GifImagePlugin._save_netpbm

Tests/helper.py

@@ -292,10 +292,6 @@ def djpeg_available() -> bool:
     return False
 
 
-def netpbm_available() -> bool:
-    return bool(shutil.which("ppmquant") and shutil.which("ppmtogif"))
-
-
 def magick_command() -> list[str] | None:
     if sys.platform == "win32":
         magickhome = os.environ.get("MAGICK_HOME")

Tests/test_file_gif.py

@@ -14,7 +14,6 @@
     assert_image_similar,
     hopper,
     is_pypy,
-    netpbm_available,
 )
 
 TYPE_CHECKING = False
@@ -397,30 +396,6 @@ def roundtrip(im: Image.Image, **kwargs: bool) -> Image.Image:
         assert_image_equal(im_rgb, reloaded)
 
 
-@pytest.mark.skipif(not netpbm_available(), reason="Netpbm not available")
-def test_save_netpbm_bmp_mode(tmp_path: Path) -> None:
-    with Image.open(TEST_GIF) as img:
-        img_rgb = img.convert("RGB")
-
-    tempfile = str(tmp_path / "temp.gif")
-    b = BytesIO()
-    GifImagePlugin._save_netpbm(img_rgb, b, tempfile)
-    with Image.open(tempfile) as reloaded:
-        assert_image_equal(img_rgb, reloaded.convert("RGB"))
-
-
-@pytest.mark.skipif(not netpbm_available(), reason="Netpbm not available")
-def test_save_netpbm_l_mode(tmp_path: Path) -> None:
-    with Image.open(TEST_GIF) as img:
-        img_l = img.convert("L")
-
-        tempfile = str(tmp_path / "temp.gif")
-        b = BytesIO()
-        GifImagePlugin._save_netpbm(img_l, b, tempfile)
-        with Image.open(tempfile) as reloaded:
-            assert_image_equal(img_l, reloaded.convert("L"))
-
-
 def test_seek() -> None:
     with Image.open("Tests/images/dispose_none.gif") as img:
         assert isinstance(img, GifImagePlugin.GifImageFile)

Tests/test_shell_injection.py

@@ -5,9 +5,9 @@
 
 import pytest
 
-from PIL import GifImagePlugin, Image, JpegImagePlugin
+from PIL import Image, JpegImagePlugin
 
-from .helper import djpeg_available, is_win32, netpbm_available
+from .helper import djpeg_available, is_win32
 
 TYPE_CHECKING = False
 if TYPE_CHECKING:
@@ -45,17 +45,3 @@ def test_load_djpeg_filename(self, tmp_path: Path) -> None:
             with Image.open(src_file) as im:
                 assert isinstance(im, JpegImagePlugin.JpegImageFile)
                 im.load_djpeg()
-
-    @pytest.mark.skipif(not netpbm_available(), reason="Netpbm not available")
-    def test_save_netpbm_filename_bmp_mode(self, tmp_path: Path) -> None:
-        with Image.open(TEST_GIF) as im:
-            im_rgb = im.convert("RGB")
-            self.assert_save_filename_check(
-                tmp_path, im_rgb, GifImagePlugin._save_netpbm
-            )
-
-    @pytest.mark.skipif(not netpbm_available(), reason="Netpbm not available")
-    def test_save_netpbm_filename_l_mode(self, tmp_path: Path) -> None:
-        with Image.open(TEST_GIF) as im:
-            im_l = im.convert("L")
-            self.assert_save_filename_check(tmp_path, im_l, GifImagePlugin._save_netpbm)

docs/releasenotes/13.0.0.rst

@@ -55,7 +55,7 @@ and so child images could only be retrieved from an :py:class:`PIL.ImageFile.Ima
 instance.
 
 Image._show
-~~~~~~~~~~~
+^^^^^^^^^^^
 
 ``Image._show`` has been removed. Use :py:meth:`~PIL.ImageShow.show` instead.
 
@@ -66,6 +66,23 @@ ImageCms.ImageCmsProfile.product_name and .product_info
 ``.product_info`` attributes have been removed. They were set to ``None`` since Pillow
 2.3.0.
 
+GifImagePlugin._save_netpbm()
+^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+
+``GifImagePlugin._save_netpbm()`` has been removed.
+
+It was never registered as a save handler by default and delegated GIF compression
+and RGB quantization to the external NetPBM ``ppmquant`` and ``ppmtogif`` utilities.
+
+Pillow's own GIF encoder writes LZW-compressed data since Pillow 8.2.0 (2021).
+Saving an ``RGB`` image as GIF converts it automatically using an adaptive 256-color
+palette since Pillow 2.4.0 (2014).
+
+To control quantization yourself, convert the image to ``P`` mode first,
+e.g. with :py:meth:`~PIL.Image.Image.quantize()`::
+
+    im.quantize(colors=256).save("out.gif")
+
 Deprecations
 ============
 

src/PIL/GifImagePlugin.py

@@ -27,8 +27,6 @@
 
 import itertools
 import math
-import os
-import subprocess
 from enum import IntEnum
 from functools import cached_property
 from typing import NamedTuple, cast
@@ -873,54 +871,6 @@ def _write_local_header(
     fp.write(o8(8))  # bits
 
 
-def _save_netpbm(im: Image.Image, fp: IO[bytes], filename: str | bytes) -> None:
-    # Unused by default.
-    # To use, uncomment the register_save call at the end of the file.
-    #
-    # If you need real GIF compression and/or RGB quantization, you
-    # can use the external NETPBM/PBMPLUS utilities.  See comments
-    # below for information on how to enable this.
-    tempfile = im._dump()
-
-    try:
-        with open(filename, "wb") as f:
-            if im.mode != "RGB":
-                subprocess.check_call(
-                    ["ppmtogif", tempfile], stdout=f, stderr=subprocess.DEVNULL
-                )
-            else:
-                # Pipe ppmquant output into ppmtogif
-                # "ppmquant 256 %s | ppmtogif > %s" % (tempfile, filename)
-                quant_cmd = ["ppmquant", "256", tempfile]
-                togif_cmd = ["ppmtogif"]
-                quant_proc = subprocess.Popen(
-                    quant_cmd, stdout=subprocess.PIPE, stderr=subprocess.DEVNULL
-                )
-                togif_proc = subprocess.Popen(
-                    togif_cmd,
-                    stdin=quant_proc.stdout,
-                    stdout=f,
-                    stderr=subprocess.DEVNULL,
-                )
-
-                # Allow ppmquant to receive SIGPIPE if ppmtogif exits
-                assert quant_proc.stdout is not None
-                quant_proc.stdout.close()
-
-                retcode = quant_proc.wait()
-                if retcode:
-                    raise subprocess.CalledProcessError(retcode, quant_cmd)
-
-                retcode = togif_proc.wait()
-                if retcode:
-                    raise subprocess.CalledProcessError(retcode, togif_cmd)
-    finally:
-        try:
-            os.unlink(tempfile)
-        except OSError:
-            pass
-
-
 # Force optimization so that we can test performance against
 # cases where it took lots of memory and time previously.
 _FORCE_OPTIMIZE = False
@@ -1215,9 +1165,3 @@ def write(self, data: Buffer) -> int:
 Image.register_save_all(GifImageFile.format, _save_all)
 Image.register_extension(GifImageFile.format, ".gif")
 Image.register_mime(GifImageFile.format, "image/gif")
-
-#
-# Uncomment the following line if you wish to use NETPBM/PBMPLUS
-# instead of the built-in "uncompressed" GIF encoder
-
-# Image.register_save(GifImageFile.format, _save_netpbm)