[FFmpeg-trac] #8861(ffmpeg:new): Creating GIF with full transparent background from PNGs with semi-transparent pixels, somehow causes this outline

[FFmpeg]

#8861: Creating GIF with full transparent background from PNGs with semi-
transparent pixels, somehow causes this outline
-------------------------------------+-------------------------------------
             Reporter:  karl-police  |                     Type:  defect
               Status:  new          |                 Priority:  wish
            Component:  ffmpeg       |                  Version:  git-
                                     |  master
             Keywords:               |               Blocked By:
             Blocking:               |  Reproduced by developer:  0
Analyzed by developer:  0            |
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 '''Summary of the bug:''' There's an unwanted outline, how can I fix it? I
 created a GIF from PNGs with semi-transparent pixels and it had this
 outline. When using transparency_color I was able to change the color, but
 I couldn't get rid of the outline.

 This doesn't happen with APNG, but APNG supports semi-transparent pixels.
 I need it as a GIF though.


 '''How to reproduce:'''
 {{{
 ffmpeg version = ffmpeg version 4.3.1
 built on downloadable .exe from ffmpeg.org
 }}}


 Commands used:
 {{{
 ffmpeg -y -i "sprite2/amongus_player_walk_00%02d.png" -lavfi
 fps=50,palettegen palette.png


 ffmpeg -i "sprite2/amongus_player_walk_00%02d.png" -i palette.png -lavfi
 "fps=50,paletteuse" -y output.gif
 }}}

 One of the original images looks like this:https://i.imgur.com/aCZxKuW.png

 the output is this: https://i.imgur.com/9iuJ14K.gif as you can see there's
 this weird outline, that I'm trying to get rid of.

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Ticket URL: <https://trac.ffmpeg.org/ticket/8861>
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