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doc/filters: add geq gradient examples

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

Also-by: Víctor Paesa <victorpaesa@googlemail.com>
Also-by: Paul Gentemann <beriukay@gmail.com>
Signed-off-by: Lou Logan <lou@lrcd.com>
This commit is contained in:
Lou Logan 2014-09-15 18:07:09 -08:00
parent 474d858fd9
commit 9c9aec33c0
1 changed files with 16 additions and 0 deletions
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doc/filters.texi
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@ -5144,6 +5144,22 @@ 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
@item
Create a radial gradient that is the same size as the input (also see
the @ref{vignette} filter):
@example
geq=lum=255*gauss((X/W-0.5)*3)*gauss((Y/H-0.5)*3)/gauss(0)/gauss(0),format=gray
@end example
@item
Create a linear gradient to use as a mask for another filter, then
compose with @ref{overlay}. In this example the video will gradually
become more blurry from the top to the bottom of the y-axis as defined
by the linear gradient:
@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
@end example
@end itemize
@section gradfun