[FFmpeg-devel] [PATCH] lavfi: add curves filter.

[Clément Bœsch]

On Tue, Mar 05, 2013 at 05:53:14PM +0000, Paul B Mahol wrote:
> On 3/5/13, Clement Boesch <ubitux at gmail.com> wrote:
> > TODO: bump minor
> > ---
> > pseudo-vintage/matrix effect: http://imgur.com/w8sQ4gw
> > Obtained with:
> >   mp=eq2=1:1.2,
> >   hue=h=20,
> >   curves=r='0.4/0.2 0.9/1':g='0.75/0.8':b='0/0.1 1/0.9'
> > ---
> >  doc/filters.texi         |  64 +++++++++
> >  libavfilter/Makefile     |   1 +
> >  libavfilter/allfilters.c |   1 +
> >  libavfilter/vf_curves.c  | 345
> > +++++++++++++++++++++++++++++++++++++++++++++++
> >  4 files changed, 411 insertions(+)
> >  create mode 100644 libavfilter/vf_curves.c
> >
> > diff --git a/doc/filters.texi b/doc/filters.texi
> > index f4c1d03..e97e974 100644
> > --- a/doc/filters.texi
> > +++ b/doc/filters.texi
> > @@ -2187,6 +2187,70 @@ indicates never reset and return the largest area
> > encountered during
> >  playback.
> >  @end table
> >
> > + at section curves
> > +
> > +Apply color adjustments using curves.
> > +
> > +This filter is similar to the Adobe Photoshop and GIMP curves tools. Each
> 
> Mentioning those two does not explain in simple terms what filter actually does.
> 

Yeah, consider it an introduction sentence. Is the following explanation
unclear?

> > +component (red, green and blue) has its values defined by @var{N} key
> > points
> > +tied from each other using a smooth curve.
> > +
> > +By default, a component curve is defined by the two points @var{(0;0)} and
> > + at var{(1;1)}. This creates a straight line where each original pixel value
> > is
> > +"adjusted" to its own value, which means no change to the image.
> > +
> > +The filter allows you to redefine these two points and add some more. A new
> > +curve (using a natural cubic spline interpolation) will be define to pass
> > +smoothly through all these new coordinates. The new defined points needs to
> > be
> > +strictly increasing over the x-axis, and their @var{x} and @var{y} values
> > must
> > +be in the @var{[0;1]} interval.  If the computed curves happened to go
> > outside
> > +the vector spaces, the values will be clipped accordingly.
> > +
> > +If there is no key point defined in @code{x=0}, the filter will
> > automatically
> > +insert a @var{(0;0)} point. In the same way, if there is no key point
> > defined
> > +in @code{x=1}, the filter will automatically insert a @var{(1;1)} point.
> > +
> > +The filter accepts parameters as a list of @var{key}=@var{value} pairs,
> > +separated by ":".
> > +
> > +A description of the accepted parameters follows.
> > +
> > + at table @option
> > + at item r, red
> > +Set the key points for the red components.
> > + at item g, green
> > +Set the key points for the green components.
> > + at item b, blue
> > +Set the key points for the red components.
> 
> typo: s/red/blue.
> 

Fixed locally.

> nit+++++++++++++: Isn't it more logical to put shorter name after longer one?
> 

Sure, whatever. Guess what, I even switched the order in the AVOption
locally :-)

[...]

-- 
Clément B.
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