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Only load new palette in putpalette() if it contains raw data #10035

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Only load new palette in putpalette() if it contains raw data #10035

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d8ca9f2
Only load new palette in putpalette() if it contains raw data
radarhere Sep 21, 2026
ec32482
Do not treat RGBA or CMYK as rawmode if it matches palette mode
radarhere Sep 21, 2026
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7 changes: 7 additions & 0 deletions Tests/test_image_putpalette.py
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Original file line number Diff line number Diff line change
Expand Up @@ -11,6 +11,9 @@ def test_putpalette() -> None:
def palette(mode: str) -> str | tuple[str, list[int]]:
im = hopper(mode).copy()
im.putpalette(list(range(256)) * 3)
assert im.palette is not None
assert im.palette.dirty

p = im.getpalette()
if p:
return im.mode, p[:10]
Expand Down Expand Up @@ -86,6 +89,8 @@ def test_putpalette_with_alpha_values() -> None:
def test_rgba_palette(mode: str, palette: tuple[int, ...]) -> None:
im = Image.new("P", (1, 1))
im.putpalette(palette, mode)
assert im.palette is not None
assert im.palette.dirty == (1 if mode == "RGBA" else 0)
assert im.getpalette() == [1, 2, 3]
assert im.palette is not None
assert im.palette.colors == {(1, 2, 3, 4): 0}
Expand All @@ -101,6 +106,8 @@ def test_rgba_palette(mode: str, palette: tuple[int, ...]) -> None:
def test_cmyk_palette(mode: str, palette: tuple[int, ...]) -> None:
im = Image.new("P", (1, 1))
im.putpalette(palette, mode)
assert im.palette is not None
assert im.palette.dirty == (1 if mode == "CMYK" else 0)
assert im.getpalette() == [250, 249, 248]
assert im.palette is not None
assert im.palette.colors == {(1, 2, 3, 4): 0}
Expand Down
5 changes: 4 additions & 1 deletion src/PIL/Image.py
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Original file line number Diff line number Diff line change
Expand Up @@ -2170,7 +2170,10 @@ def putpalette(
self.palette.mode = "CMYK"
elif "A" in rawmode:
self.palette.mode = "RGBA"
self.load() # install new palette
if self.palette.mode == self.palette.rawmode:
self.palette.rawmode = None
if self.palette.rawmode:
self.load() # decode raw palette data

def putpixel(
self,
Expand Down
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