[FFmpeg-trac] #1279(avfilter:open): Transform X'Y'Z' to RGB via colormatrix (was: Transform X'Y'Z' to RGB via lutrgb)

[FFmpeg]

#1279: Transform X'Y'Z' to RGB via colormatrix
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             Reporter:  wolfgangw    |                    Owner:
                 Type:  enhancement  |                   Status:  open
             Priority:  wish         |                Component:  avfilter
              Version:  git-master   |               Resolution:
             Keywords:  XYZ j2k lut  |               Blocked By:
  colormatrix                        |  Reproduced by developer:  0
             Blocking:               |
Analyzed by developer:  0            |
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Description changed by richardpl:

Old description:

> Hi, thanks for an awesome toolset.
>
> In order to do a colorspace transform (like X'Y'Z' to RGB) one would need
> to apply a 3x3 transformation matrix. It would be a very handy feature if
> one could do this in lutrgb. Like
>
> ffplay -vf lutrgb="r=r*3.2404542 + g*-1.5371385 +
> b*-0.4985314:g=r*-0.9692660 + g*1.8760108 + b*0.0415560:b=r*0.0556434 +
> g*-0.2040259 + b*1.0572252" <some file in XYZ>
>
> which is not possible as of current git master: 'r', 'g' and 'b' are not
> valid right-hand-side expressions.
>
> Looking at libavfilter/vf_lut.c suggests that this might even be quite
> easy to add. Anyone likes to jump on it before I break too much porcelain
> (I don't know the codebase well enough now)?
>
> Again, thanks for FFMpeg.
> Wolfgang

New description:

 In order to do a colorspace transform (like X'Y'Z' to RGB) one would need
 to apply a 3x3 transformation matrix. It would be a very handy feature if
 one could do this in colormatrix.

 Removed vf_lut nonsense as it is very slow approach.

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Ticket URL: <https://ffmpeg.org/trac/ffmpeg/ticket/1279#comment:19>
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