[FFmpeg-trac] #831(avcodec:closed): gif: 1bpp with transparency decodes to black screen
FFmpeg
trac at avcodec.org
Mon Dec 26 01:45:32 CET 2011
#831: gif: 1bpp with transparency decodes to black screen
------------------------------------+-----------------------------------
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 |
------------------------------------+-----------------------------------
Changes (by cehoyos):
* keywords: => bmp alpha
* resolution: => invalid
* status: new => closed
* component: undetermined => avcodec
* version: unspecified => git-master
Comment:
The sample has a two-colour palette: Solid black and transparent black.
It is transcoded correctly with
ffmpeg -i 1bpp_transparent_white.gif out.png
ffmpeg -i 1bpp_transparent_white.gif -pix_fmt bgra out.png
ffmpeg -i 1bpp_transparent_white.gif -f image2 out.gif
I will attach a patch that allows to do the following:
ffmpeg -i 1bpp_transparent_white.gif out.bmp
ffmpeg -i out.bmp out.png
and get the same (semi-transparent) png as above.
But since neither ImageMagick nor GIMP show out.bmp (with the patch) as
semi-transparent, I am not sure if any application supports transparency
in the bmp palette (and the Microsoft documentation repeatedly states the
relevant value "must be zero" making a bug in FFmpeg's bmp palette reading
code likely).
Otoh, it is possible that for ImageMagick and GIMP, this depends on the
BITMAPHEADER version, so please reopen if you find a palletized bmp that
shows transparency with any application.
--
Ticket URL: <http://www.avcodec.org/trac/ffmpeg/ticket/831#comment:1>
FFmpeg <http://ffmpeg.org>
FFmpeg issue tracker
More information about the FFmpeg-trac
mailing list