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PNG palette transparency

https://magick.imagemagick.org/viewtopic.php?t=17635

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PNG palette transparency

Posted: 2010-12-07T17:51:47-07:00
by GreenKoopa
Original post: Composite with different transparencies
anthony wrote: However a recent change was that IM is attempting to generate smaller PNG pallette image (with multiple levels of alpha). However in this case it is failing to preserve alpha!!!!!

This is a known BUG but you should report this (as a new topic) the BUG forum with pointers to the original image, and probably to this post. Probably notify 'glennrp' of the PNG failure in this case. with a pointer to that BUG topic.
Compositing two transparent pixels results in black:
composite USAsnow4.png transp_rain4.png finalimg.png

These work fine:
composite USAsnow4.png transp_rain4.png PNG32:finalimg.png
composite transp_rain4.png USAsnow4.png finalimg.png

Re: PNG palette transparency

Posted: 2010-12-07T18:26:18-07:00
by GreenKoopa
My ImageMagick came from a zip file labeled 6.6.6-2 but reports as 6.6.6-3 2010-12-01 Q16. I am using the Windows portable version.
weatherbadger reports my PNG32: workaround not working in 6.6.1-0 2010-07-29

A seeming related problem:
viewtopic.php?f=3&t=17631

Re: PNG palette transparency

Posted: 2010-12-07T19:51:09-07:00
by GreenKoopa
I verified that I really have "6.6.6-3 2010-12-01 Q16" an re-ran some tests.

Doesn't work (transparent turn to balck):
composite USAsnow4.png transp_rain4.png a.png
composite USAsnow4.png transp_rain4.png -type TrueColorMatte b.png

Works:
composite USAsnow4.png transp_rain4.png -define png:color-type=6 c.png
composite USAsnow4.png transp_rain4.png PNG32:d.png
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