[FFmpeg-devel] [PATCH v2] doc/filters: add geq gradient examples

[Lou Logan]

On Tue, 16 Sep 2014 07:34:14 +0200, Clément Bœsch wrote:

> On Mon, Sep 15, 2014 at 06:56:29PM -0800, Lou Logan wrote:
> > + at item
> > +Create a radial gradient that is the same size as the input:
> > + at example
> > +geq=lum=255*gauss((X/W-0.5)*3)*gauss((Y/H-0.5)*3)/gauss(0)/gauss(0),format=gray
> > + at end example
> > +
> 
> You may mention @ref{vignette} filter here so people don't end up using it
> verbatim.

Mentioned.

> > + at item
> > +Create a linear gradient to use as a mask for another filter, then
> > +compose with @ref{overlay}:
> > + at example
> > +geq=lum=255*(Y/H),format=gray[grad];[0:v]boxblur=4[blur];[blur][grad]alphamerge[alpha];[0:v][alpha]overlay
> 
> This filtergraph is complex and very input dependant; please provide a
> complete command line as an example

Added. I actually prefer complete examples.


New version inserted below:

From 3ec5557f7ffd4e2ce6ddc5c06d1e5d5d07013536 Mon Sep 17 00:00:00 2001
From: Lou Logan <lou at lrcd.com>
Date: Mon, 15 Sep 2014 18:07:09 -0800
Subject: [PATCH] doc/filters: add geq gradient examples
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit

Radial gradient by Víctor Paesa.
Linear gradient by Paul Gentemann.

Also-by: Víctor Paesa <victorpaesa at googlemail.com>
Also-by: Paul Gentemann <beriukay at gmail.com>
Signed-off-by: Lou Logan <lou at lrcd.com>
---
 doc/filters.texi | 14 ++++++++++++++
 1 file changed, 14 insertions(+)

diff --git a/doc/filters.texi b/doc/filters.texi
index bb486ea..1881b5c 100644
--- a/doc/filters.texi
+++ b/doc/filters.texi
@@ -5124,6 +5124,20 @@ Modify RGB components depending on pixel position:
 @example
 geq=r='X/W*r(X,Y)':g='(1-X/W)*g(X,Y)':b='(H-Y)/H*b(X,Y)'
 @end example
+
+ at item
+Create a radial gradient that is the same size as the input (also see
+the @ref{vignette} filter):
+ at example
+geq=lum=255*gauss((X/W-0.5)*3)*gauss((Y/H-0.5)*3)/gauss(0)/gauss(0),format=gray
+ at end example
+
+ at item
+Create a linear gradient to use as a mask for another filter, then
+compose with @ref{overlay}:
+ at example
+ffmpeg -i input.mp4 -filter_complex "geq=lum=255*(Y/H),format=gray[grad];[0:v]boxblur=4[blur];[blur][grad]alphamerge[alpha];[0:v][alpha]overlay" output.mp4
+ at end example
 @end itemize
 
 @section gradfun
-- 
2.1.0