[FFmpeg-trac] #5397(avfilter:open): Incorrect curves filter work

FFmpeg trac at avcodec.org
Fri Jul 22 03:33:25 EEST 2016

#5397: Incorrect curves filter work
             Reporter:  Ilya87      |                    Owner:
                 Type:  defect      |                   Status:  open
             Priority:  normal      |                Component:  avfilter
              Version:  git-master  |               Resolution:
             Keywords:  curves      |               Blocked By:
             Blocking:              |  Reproduced by developer:  1
Analyzed by developer:  1           |

Comment (by ubitux):

 Replying to [comment:9 Ilya87]:
 > And what if I define not only 2 points (start point 0.037516/0 and 1/1)
 on channel, but more? For example,
 > {{{
 > -vf curves=r='0.037516/0 0.127516/0.4 1/1'
 > }}}
 > Will it work in Gimp-style?

 Unfortunately no. It matches Photoshop behavior. I'm attaching 3 new
 images so you can compare the 3 tools. But basically, you can assume
 FFmpeg always matches Photoshop.

 Also, you can try this branch:
 https://github.com/ubitux/FFmpeg/compare/curves (note to future reader: if
 this branch doesn't exist anymore, it's probably merged upstream).

 Commit 2/2 of this branch adds a "plot" option you can use to get the
 curves used by FFmpeg. Quoting the example from the documentation:

 ffmpeg -f lavfi -i color -vf curves=cross_process:plot=/tmp/curves.plt
 -frames:v 1 -f null -
 gnuplot -p /tmp/curves.plt

Ticket URL: <https://trac.ffmpeg.org/ticket/5397#comment:10>
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