[FFmpeg-user] How to add alpha channel to normal png image

[qw]

At 2015-06-28 17:11:03, "Paul B Mahol" <onemda at gmail.com> wrote:
>Dana 28. 6. 2015. 09:31 osoba "qw" <applemax82 at 163.com> napisala je:
>>
>> Hi,
>>
>>
>> PNG format supports alpha channel, but some png images don't have alpha
>channel. How to add alpha channel to those png images and set alpha value?
>>
>>
>
>See colorkey filter documentation.
>
I use the below command to run colorkey filter, and ffmpeg report there is no colorkey filter:
ffmpeg -i ./image.png -vf colorkey=green ./output.png


ffmpeg version 2.7.1 Copyright (c) 2000-2015 the FFmpeg developers
  built with gcc 4.4.7 (GCC) 20120313 (Red Hat 4.4.7-11)
  configuration: --enable-gpl --enable-libx264
  libavutil      54. 27.100 / 54. 27.100
  libavcodec     56. 41.100 / 56. 41.100
  libavformat    56. 36.100 / 56. 36.100
  libavdevice    56.  4.100 / 56.  4.100
  libavfilter     5. 16.101 /  5. 16.101
  libswscale      3.  1.101 /  3.  1.101
  libswresample   1.  2.100 /  1.  2.100
  libpostproc    53.  3.100 / 53.  3.100
Input #0, png_pipe, from './transparent_3.png':
  Duration: N/A, bitrate: N/A
    Stream #0:0: Video: png, rgba(pc), 256x256, 25 tbr, 25 tbn, 25 tbc
[AVFilterGraph @ 0x1d1e900] No such filter: 'colorkey'
Error opening filters!


which version of ffmpeg has colorkey filter?






At 2015-06-28 17:11:03, "Paul B Mahol" <onemda at gmail.com> wrote:
>Dana 28. 6. 2015. 09:31 osoba "qw" <applemax82 at 163.com> napisala je:
>>
>> Hi,
>>
>>
>> PNG format supports alpha channel, but some png images don't have alpha
>channel. How to add alpha channel to those png images and set alpha value?
>>
>>
>
>See colorkey filter documentation.
>
>> Thanks!
>>
>>
>> B.R.
>>
>>
>> Andrew
>> _______________________________________________
>> ffmpeg-user mailing list
>> ffmpeg-user at ffmpeg.org
>> http://ffmpeg.org/mailman/listinfo/ffmpeg-user
>_______________________________________________
>ffmpeg-user mailing list
>ffmpeg-user at ffmpeg.org
>http://ffmpeg.org/mailman/listinfo/ffmpeg-user