[FFmpeg-trac] #769(swscale:closed): png gray8 alpha decodes incorrectly

[FFmpeg]

#769: png gray8 alpha decodes incorrectly
-------------------------------------+-------------------------------------
             Reporter:  ami_stuff    |                    Owner:
                 Type:  defect       |                   Status:  closed
             Priority:  normal       |                Component:  swscale
              Version:  git-master   |               Resolution:  fixed
             Keywords:  gray8a       |               Blocked By:
  alpha png                          |  Reproduced by developer:  1
             Blocking:               |
Analyzed by developer:  0            |
-------------------------------------+-------------------------------------

Comment (by cehoyos):

 The transparency information of basi4a08.png gets lost with the following
 command:
 {{{
 $ ffmpeg -i basi4a08.png -pix_fmt rgba out.png
 ffmpeg version N-43716-g92b8c9d Copyright (c) 2000-2012 the FFmpeg
 developers
   built on Aug 18 2012 18:47:44 with gcc 4.6.1 (GCC)
   configuration: --cc=/usr/local/gcc-4.6.1/bin/gcc
   libavutil      51. 70.100 / 51. 70.100
   libavcodec     54. 53.100 / 54. 53.100
   libavformat    54. 25.104 / 54. 25.104
   libavdevice    54.  2.100 / 54.  2.100
   libavfilter     3. 11.101 /  3. 11.101
   libswscale      2.  1.101 /  2.  1.101
   libswresample   0. 15.100 /  0. 15.100
 Input #0, image2, from 'basi4a08.png':
   Duration: 00:00:00.04, start: 0.000000, bitrate: N/A
     Stream #0:0: Video: png, gray8a, 32x32, 25 tbr, 25 tbn, 25 tbc
 Output #0, image2, to 'out.png':
   Metadata:
     encoder         : Lavf54.25.104
     Stream #0:0: Video: png, rgba, 32x32, q=2-31, 200 kb/s, 90k tbn, 25
 tbc
 Stream mapping:
   Stream #0:0 -> #0:0 (png -> png)
 Press [q] to stop, [?] for help
 frame=    1 fps=0.0 q=0.0 Lsize=       0kB time=00:00:00.04 bitrate=
 0.0kbits/s
 video:0kB audio:0kB subtitle:0 global headers:0kB muxing overhead
 -100.000000%
 }}}

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Ticket URL: <https://ffmpeg.org/trac/ffmpeg/ticket/769#comment:12>
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