Merge pull request #6596 from PososikTeam/fix-padding

Improved palette handling in ImageOps

Tests/test_imageops.py

@@ -149,6 +149,21 @@ def test_pad_round():
     assert new_im.load()[0, 2] == 1
 
 
+@pytest.mark.parametrize("mode", ("P", "PA"))
+def test_palette(mode):
+    im = hopper(mode)
+
+    # Expand
+    expanded_im = ImageOps.expand(im)
+    assert_image_equal(im.convert("RGB"), expanded_im.convert("RGB"))
+
+    # Pad
+    padded_im = ImageOps.pad(im, (256, 128), centering=(0, 0))
+    assert_image_equal(
+        im.convert("RGB"), padded_im.convert("RGB").crop((0, 0, 128, 128))
+    )
+
+
 def test_pil163():
     # Division by zero in equalize if < 255 pixels in image (@PIL163)
 

src/PIL/ImageOps.py

@@ -21,7 +21,7 @@
 import operator
 import re
 
-from . import Image
+from . import Image, ImagePalette
 
 #
 # helpers
@@ -291,6 +291,8 @@ def pad(image, size, method=Image.Resampling.BICUBIC, color=None, centering=(0.5
         out = resized
     else:
         out = Image.new(image.mode, size, color)
+        if resized.palette:
+            out.putpalette(resized.getpalette())
         if resized.width != size[0]:
             x = round((size[0] - resized.width) * max(0, min(centering[0], 1)))
             out.paste(resized, (x, 0))
@@ -396,9 +398,8 @@ def expand(image, border=0, fill=0):
     width = left + image.size[0] + right
     height = top + image.size[1] + bottom
     color = _color(fill, image.mode)
-    if image.mode == "P" and image.palette:
-        image.load()
-        palette = image.palette.copy()
+    if image.palette:
+        palette = ImagePalette.ImagePalette(palette=image.getpalette())
         if isinstance(color, tuple):
             color = palette.getcolor(color)
     else: