Set default resize sampling for I;16* images to BICUBIC

Author: radarhere

Tests/test_image_resize.py

@@ -315,14 +315,14 @@ def test_transposed(self) -> None:
             im = im.resize((64, 64))
             assert im.size == (64, 64)
 
-    @pytest.mark.parametrize("mode", ("L", "RGB", "I", "F"))
+    @pytest.mark.parametrize(
+        "mode", ("L", "RGB", "I", "I;16", "I;16L", "I;16B", "I;16N", "F")
+    )
     def test_default_filter_bicubic(self, mode: str) -> None:
         im = hopper(mode)
         assert im.resize((20, 20), Image.Resampling.BICUBIC) == im.resize((20, 20))
 
-    @pytest.mark.parametrize(
-        "mode", ("1", "P", "I;16", "I;16L", "I;16B", "BGR;15", "BGR;16")
-    )
+    @pytest.mark.parametrize("mode", ("1", "P", "BGR;15", "BGR;16"))
     def test_default_filter_nearest(self, mode: str) -> None:
         im = hopper(mode)
         assert im.resize((20, 20), Image.Resampling.NEAREST) == im.resize((20, 20))

docs/releasenotes/11.0.0.rst

@@ -119,10 +119,11 @@ Specific WebP Feature Checks
 API Changes
 ===========
 
-TODO
-^^^^
+Default resampling filter for I;16* image modes
+^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
 
-TODO
+The default resampling filter for I;16, I;16L, I;16B and I;16N has been changed from
+``Image.NEAREST`` to ``Image.BICUBIC``, to match the majority of modes.
 
 API Additions
 =============

src/PIL/Image.py

@@ -2278,8 +2278,8 @@ def resize(
            :py:data:`Resampling.BILINEAR`, :py:data:`Resampling.HAMMING`,
            :py:data:`Resampling.BICUBIC` or :py:data:`Resampling.LANCZOS`.
            If the image has mode "1" or "P", it is always set to
-           :py:data:`Resampling.NEAREST`. If the image mode specifies a number
-           of bits, such as "I;16", then the default filter is
+           :py:data:`Resampling.NEAREST`. If the image mode is "BGR;15",
+           "BGR;16" or "BGR;24", then the default filter is
            :py:data:`Resampling.NEAREST`. Otherwise, the default filter is
            :py:data:`Resampling.BICUBIC`. See: :ref:`concept-filters`.
         :param box: An optional 4-tuple of floats providing
@@ -2302,8 +2302,8 @@ def resize(
         """
 
         if resample is None:
-            type_special = ";" in self.mode
-            resample = Resampling.NEAREST if type_special else Resampling.BICUBIC
+            bgr = self.mode.startswith("BGR;")
+            resample = Resampling.NEAREST if bgr else Resampling.BICUBIC
         elif resample not in (
             Resampling.NEAREST,
             Resampling.BILINEAR,