Fix invalid PNG bit depth when using deprecated --colours arg#4971
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jcupitt merged 1 commit intolibvips:masterfrom Mar 31, 2026
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ceil(log2(colours)) can produce non-power-of-two values (e.g. 5 for --colours 32) which libpng rejects. Use g_bit_storage() to compute the minimum bits needed, then round up to a valid PNG palette bit depth (1, 2, 4, or 8).
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@jcupitt Can I merge this simple fix? |
jcupitt
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Mar 31, 2026
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Sorry @felixbuenemann! Done. |
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ceil(log2(colours))can produce non-power-of-two values (e.g. 5 for--colours 32) which libpng rejects.Use
g_bit_storage()to compute the minimum bits needed, then round up to a valid PNG palette bit depth (1, 2, 4, or 8).