[FFmpeg-trac] #8588(avfilter:new): Palettegen adds one color on transparent input
FFmpeg
trac at avcodec.org
Sun Mar 29 23:04:29 EEST 2020
#8588: Palettegen adds one color on transparent input
-------------------------------------+-------------------------------------
Reporter: RedError | Type: defect
Status: new | Priority: normal
Component: avfilter | Version: git-
Keywords: palettegen | master
color transparency gif png alpha | Blocked By:
Blocking: | Reproduced by developer: 0
Analyzed by developer: 0 |
-------------------------------------+-------------------------------------
Summary of the bug:
[https://github.com/FFmpeg/FFmpeg/blob/master/libavfilter/vf_palettegen.c
palettegen] from a transparent gif, png, adds the invisible transparency
color to the palette as a visible color, with no relation to the one
selected with the transparency_color option.
On transparent PNG, it will use the rgb value of the transparent areas.
On transparent GIF, it will always add white.
None of the available [https://ffmpeg.org/ffmpeg-filters.html#palettegen-1
options] seem to change that.
How to reproduce:
{{{
ffmpeg -i "transparent.gif" -vf palettegen "palette.png" -y
}}}
Of course, using that palette with paletteuse will use the added color in
the result, as paletteuse has no way of knowing that it was actually a
transparent color.
{{{
ffmpeg -i "target.png" -i "palette.png" -lavfi paletteuse=dither=0
"target_merged.gif"
}}}
This will randomly add one color where there shouldn't be one.
--
Ticket URL: <https://trac.ffmpeg.org/ticket/8588>
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