doc/filters: state negate filter's option
authorGyan Doshi <ffmpeg@gyani.pro>
Thu, 5 Jul 2018 14:06:32 +0000 (19:36 +0530)
committerGyan Doshi <ffmpeg@gyani.pro>
Thu, 5 Jul 2018 14:08:09 +0000 (19:38 +0530)
commit4cd5c3f9ec7859503d733ba7b5ab23994c1b2fc5
treedc4b7b771327e3db8094e064e02de00f7b1aad5c
parent5aba5b89d0b1d73164d3b81764828bb8b20ff32a
doc/filters: state negate filter's option

Also clarify that the negate_alpha option is a boolean
doc/filters.texi