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Ensure Image and core palettes are in sync after PA conversion #9834

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Ensure Image and core palettes are in sync after PA conversion #9834

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39c5152
Add xfailing test for pa2p quirk
akx Jul 29, 2026
31693e6
Ensure Image and core palettes are in sync after PA conversion (alpha…
akx Jul 29, 2026
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12 changes: 12 additions & 0 deletions Tests/test_image_convert.py
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Original file line number Diff line number Diff line change
Expand Up @@ -357,3 +357,15 @@ def test_matrix_identity() -> None:
# Assert
# No change
assert_image_equal(converted_im, im)


def test_pa2p_truly_drops_alpha() -> None:
im = Image.frombytes("P", (2, 1), bytes([0, 1])).convert("PA")
im.putpalette(bytes([255, 0, 0, 7, 0, 255, 0, 9]), "RGBA")
im.putalpha(Image.frombytes("L", (2, 1), bytes([240, 220])))
assert im.get_flattened_data() == ((0, 240), (1, 220)) # Matches the alpha band
im_p = im.convert("P")
assert im_p.palette is not None
assert im_p.im.getpalettemode() == im_p.palette.mode == "RGB"
rgba_data = im_p.convert("RGBA").get_flattened_data()
assert rgba_data == ((255, 0, 0, 255), (0, 255, 0, 255))
5 changes: 2 additions & 3 deletions src/PIL/Image.py
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Expand Up @@ -1242,9 +1242,8 @@ def convert_transparency(

new_im = self._new(im)
if mode in ("P", "PA") and palette != Palette.ADAPTIVE:
from . import ImagePalette

new_im.palette = ImagePalette.ImagePalette("RGB", im.getpalette("RGB"))
# Install the original image's palette into the new copy
new_im.putpalette(im.getpalette("RGB"))
if delete_trns:
# crash fail if we leave a bytes transparency in an rgb/l mode.
del new_im.info["transparency"]
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