Re: Unable to preserve binary transparency with PNG8

----- Juraj Komacka <[email protected]> wrote:
> Hi,
> 
> having an image with binary transparency I am unable to convert it to PNG8
> without loosing it.
> [...]
>       libpng-1.2.50 warning: Invalid background palette index
> 
> Am I missing something?
> 
> Using ImageMagick 6.8.9-9 Q16, everything works as expected (same commands,
> just remove gm from them)

It's a bug in GM's palette-building in coders/png.c

I maintain coders/png.c in both IM and GM, but they've evolved along different
paths so a simple port from one to the other is no longer possible.  Fixing
the bug seems to require a major rewrite of coders/png.c in GM, and I've
got to be careful to copy only parts of coders/png.c that I wrote myself.
I don't have much hope that this bug will be fixed in the near future.

Glenn

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