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Merged
radarhere merged 2 commits into from
Nov 6, 2026
+20 −0
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Improve converting images with transparency to PA #10421

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fce6c8c
Fix converting images with transparency to PA
qodelicious Nov 5, 2026
c798abc
Rearrange code
radarhere Nov 6, 2026
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14 changes: 14 additions & 0 deletions Tests/test_image_convert.py
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Original file line number Diff line number Diff line change
Expand Up @@ -317,6 +317,20 @@ def test_p2pa_palette() -> None:
assert im_pa.getpalette(None) == im.getpalette()


@pytest.mark.parametrize(
"mode, value",
(("1", 255), ("L", 128), ("RGB", (1, 2, 3)), ("I;16", 0x1234), ("I", 0x12345)),
)
def test_trns_to_pa(mode: str, value: int | tuple[int, int, int]) -> None:
im = Image.new(mode, (2, 1))
im.putpixel((1, 0), value)
im.info["transparency"] = value

im_pa = im.convert("PA")
assert "transparency" not in im_pa.info
assert im_pa.getchannel("A").get_flattened_data() == (255, 0)


rgb2xyz_matrix = (
0.412453, 0.357580, 0.180423, 0,
0.212671, 0.715160, 0.072169, 0,
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6 changes: 6 additions & 0 deletions src/PIL/Image.py
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Original file line number Diff line number Diff line change
Expand Up @@ -1198,6 +1198,12 @@ def convert_transparency(
else:
msg = "Transparency for P mode should be bytes or int"
raise ValueError(msg)
elif self.mode in {"1", "L", "I", "I;16", "RGB"} and mode == "PA":
im_without_trns = self.copy()
del im_without_trns.info["transparency"]
new_im = im_without_trns.convert(mode, dither=dither)
new_im.putalpha(self.convert("RGBA").getchannel("A"))
return new_im

if mode == "P" and palette == Palette.ADAPTIVE:
im = self.im.quantize(colors)
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