Apply dither when converting/quantizing to an adaptive palette - #9859
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83Gh0st wants to merge 1 commit into
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Apply dither when converting/quantizing to an adaptive palette#985983Gh0st wants to merge 1 commit into
83Gh0st wants to merge 1 commit into
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Fixes python-pillow#5836. dither was silently ignored whenever no reference palette was given, since the underlying quantize() has no dither support without one. Now re-converts through the computed palette when dithering is explicitly requested.
radarhere
reviewed
Aug 12, 2026
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Fixes #5836.
ditherwas silently ignored whenever no referencepalettewas given (e.g.im.convert("P", palette=Image.Palette.ADAPTIVE, dither=...)or plainim.quantize(dither=...)), because the underlyingself.im.quantize()C call has no dithering support without an explicit reference palette. This re-converts through the computed adaptive palette when dithering is explicitly requested, soditheris honored in bothconvert()andquantize(). Calls that don't passditherare unaffected.Changes proposed in this pull request:
Image.convert(..., palette=Palette.ADAPTIVE, dither=...)Image.quantize(..., dither=...)when no reference palette is given