[FFmpeg-trac] #831(avcodec:closed): gif: 1bpp with transparency decodes to black screen

[FFmpeg]

#831: gif: 1bpp with transparency decodes to black screen
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             Reporter:  ami_stuff   |                    Owner:
                 Type:  defect      |                   Status:  closed
             Priority:  normal      |                Component:  avcodec
              Version:  git-master  |               Resolution:  invalid
             Keywords:  bmp alpha   |               Blocked By:
             Blocking:              |  Reproduced by developer:  0
Analyzed by developer:  0           |
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Comment (by beastd):

 Hi!

 @cehoyos:
 The patch is IMHO, as you already pointed yourself, not a good idea.
 Some picky readers might not accept the files and if Microsoft ever
 decides to extend the format in
 that place the FFmpeg generated files might be invalid or misinterpreted
 (rather unlikely but still).

 Perhaps a new functionality that makes it possible for users to specify a
 background color
 (or even picture) against which the transparent colors should be evaluated
 would be a good thing.
 E.g. the user could choose white and would therefore end up in this
 example with the fully transparent
 black palette entry translated to white (0xFF000000 would be translated to
 0x00FFFFFF in the palette).

 @ami_stuff:
 If you are interested, a new ticket with type enhancement could be opened
 so it isn't forgotten. Otherwise as I can't say how difficult it is to
 implement such a feature in current FFmpeg, I would say we just let it be
 for now.

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Ticket URL: <https://ffmpeg.org/trac/ffmpeg/ticket/831#comment:2>
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