Do not pad PNG palette when saving if bits is specified - #10029
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When saving a P mode image as PNG with an explicit bits argument, Pillow has always padded the PLTE (and tRNS) chunks with zeroes up to 2 ** bits entries. This adds an opt-in palette_padding=False option so only the actual palette entries are written, per issue #10028. Defaults to True, preserving existing behavior. Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>
Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>
Drop the palette_padding option and always trim the PLTE/tRNS chunks to the palette's actual size, matching the non-explicit-bits path, which has done this since #5330 (2021) with no compatibility issues. Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>
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Fixes #10028.
Adds an opt-inpalette_padding=FalsePNG save option so thePLTE/tRNSchunks aren't padded up to2 ** bitsentries whenbitsis explicitly specified.Defaults toTrue, preserving current behavior.