[FFmpeg-devel] [PATCH] lavfi: add colorlevels filter

[Clément Bœsch]

On Wed, Dec 10, 2014 at 02:26:51PM +0000, Paul B Mahol wrote:
> Signed-off-by: Paul B Mahol <onemda at gmail.com>
> ---
>  doc/filters.texi             |  41 +++++++
>  libavfilter/Makefile         |   1 +
>  libavfilter/allfilters.c     |   1 +
>  libavfilter/vf_colorlevels.c | 254 +++++++++++++++++++++++++++++++++++++++++++
>  4 files changed, 297 insertions(+)
>  create mode 100644 libavfilter/vf_colorlevels.c
> 
> diff --git a/doc/filters.texi b/doc/filters.texi
> index 0ea3955..444dfda 100644
> --- a/doc/filters.texi
> +++ b/doc/filters.texi
> @@ -2934,6 +2934,47 @@ colorbalance=rs=.3
>  @end example
>  @end itemize
>  
> + at section colorlevels
> +
> +Adjust video input frames using levels.
> +
> +The filter accepts the following options:
> +
> + at table @option
> + at item rimim
> + at item gimin
> + at item bimin
> + at item aimin
> +Adjust red, green, blue and alpha input black point.
> +Allowed ranges for options are @code{[-1.0, 1.0]}. Defaults are @code{0}.
> +
> + at item rimax
> + at item gimax
> + at item bimax
> + at item aimax
> +Adjust red, green, blue and alpha input white point.
> +Allowed ranges for options are @code{[-1.0, 1.0]}. Defaults are @code{1}.
> +
> +Input levels are used to lighten highlights (bright tones), darken shadows
> +(dark tones), change the balance of bright and dark tones.
> +
> + at item romim
> + at item gomin
> + at item bomin
> + at item aomin
> +Adjust red, green, blue and alpha output black point.
> +Allowed ranges for options are @code{[0, 1.0]}. Defaults are @code{0}.
> +
> + at item romax
> + at item gomax
> + at item bomax
> + at item aomax
> +Adjust red, green, blue and alpha output white point.
> +Allowed ranges for options are @code{[0, 1.0]}. Defaults are @code{1}.
> +
> +Output levels allows manual selection of a constrained output level range.
> + at end table
> +

One of the most common usage for the color levels is to have an automatic
adjustment of the range on the luma level.

Typically, doing this: https://lut.im/OiNweWNU/MraUtDBe using a threshold
on both side.

Maybe you want to add such feature later thought.

[...]

-- 
Clément B.
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