From 75b67a8a99202321e9241e29c98c633a1b20846b Mon Sep 17 00:00:00 2001 From: Stefano Sabatini Date: Sat, 25 Sep 2010 01:18:43 +0000 Subject: Make the crop filters accept parametric expressions. Originally committed as revision 25185 to svn://svn.ffmpeg.org/ffmpeg/trunk --- doc/filters.texi | 103 +++++++++++++++++++++++++++++++++++++++++++++---------- 1 file changed, 85 insertions(+), 18 deletions(-) (limited to 'doc/filters.texi') diff --git a/doc/filters.texi b/doc/filters.texi index f934082d9a..1dc222a119 100644 --- a/doc/filters.texi +++ b/doc/filters.texi @@ -26,34 +26,101 @@ Below is a description of the currently available video filters. @section crop -Crop the input video to @var{width}:@var{height}:@var{x}:@var{y}. +Crop the input video to @var{out_w}:@var{out_h}:@var{x}:@var{y}. -@example -./ffmpeg -i in.avi -vf "crop=0:240:0:0" out.avi -@end example +The parameters are expressions containing the following constants: -The @var{width} and @var{height} parameters specify the width and height -of the output (non-cropped) area. +@table @option +@item E, PI, PHI +the corresponding mathematical approximated values for e +(euler number), pi (greek PI), PHI (golden ratio) -A value of 0 is interpreted as the maximum possible size contained in -the area delimited by the top-left corner at position x:y. +@item x, y +the computed values for @var{x} and @var{y}. They are evaluated for +each new frame. -@var{x} and @var{y} specify the position of the top-left corner of the -output (non-cropped) area. +@item in_w, in_h +the input width and heigth -The default value of @var{x} and @var{y} is 0. +@item iw, ih +same as @var{in_w} and @var{in_h} + +@item out_w, out_h +the output (cropped) width and heigth + +@item ow, oh +same as @var{out_w} and @var{out_h} + +@item n +the number of input frame, starting from 0 + +@item pos +the position in the file of the input frame, NAN if unknown + +@item t +timestamp expressed in seconds, NAN if the input timestamp is unknown + +@end table + +The @var{out_w} and @var{out_h} parameters specify the expressions for +the width and height of the output (cropped) video. They are +evaluated just at the configuration of the filter. + +The default value of @var{out_w} is "in_w", and the default value of +@var{out_h} is "in_h". -For example the parameters: +The expression for @var{out_w} may depend on the value of @var{out_h}, +and the expression for @var{out_h} may depend on @var{out_w}, but they +cannot depend on @var{x} and @var{y}, as @var{x} and @var{y} are +evaluated after @var{out_w} and @var{out_h}. +The @var{x} and @var{y} parameters specify the expressions for the +position of the top-left corner of the output (non-cropped) area. They +are evaluated for each frame. If the evaluated value is not valid, it +is approximated to the nearest valid value. + +The default value of @var{x} is "(in_w-out_w)/2", and the default +value for @var{y} is "(in_h-out_h)/2", which set the cropped area at +the center of the input image. + +The expression for @var{x} may depend on @var{y}, and the expression +for @var{y} may depend on @var{x}. + +Follow some examples: @example -"crop=0:0:100:100" -@end example +# crop the central input area with size 100x100 +crop=100:100 -will delimit the rectangle with the top-left corner placed at position -100:100 and the right-bottom corner corresponding to the right-bottom -corner of the input image. +# crop the central input area with size 2/3 of the input video +"crop=2/3*in_w:2/3*in_h" -The default value of @var{width} and @var{height} is 0. +# crop the input video central square +crop=in_h + +# delimit the rectangle with the top-left corner placed at position +# 100:100 and the right-bottom corner corresponding to the right-bottom +# corner of the input image. +crop=in_w-100:in_h-100:100:100 + +# crop 10 pixels from the lefth and right borders, and 20 pixels from +# the top and bottom borders +"crop=in_w-2*10:in_h-2*20" + +# keep only the bottom right quarter of the input image +"crop=in_w/2:in_h/2:in_w/2:in_h/2" + +# crop height for getting Greek harmony +"crop=in_w:1/PHI*in_w" + +# trembling effect +"crop=in_w/2:in_h/2:(in_w-out_w)/2+((in_w-out_w)/2)*sin(n/10):(in_h-out_h)/2 +((in_h-out_h)/2)*sin(n/7)" + +# erratic camera effect depending on timestamp and position +"crop=in_w/2:in_h/2:(in_w-out_w)/2+((in_w-out_w)/2)*sin(t*10):(in_h-out_h)/2 +((in_h-out_h)/2)*sin(t*13)" + +# set x depending on the value of y +"crop=in_w/2:in_h/2:y:10+10*sin(n/10)" +@end example @section fifo -- cgit v1.2.3