avfilter: add unpremultiply filter

Signed-off-by: Paul B Mahol <onemda@gmail.com>

1 files changed, 19 insertions, 0 deletions

diff --git a/doc/filters.texi b/doc/filters.texi
index 4089135807..96abffbbdd 100644
--- a/doc/filters.texi
+++ b/doc/filters.texi
@@ -14532,6 +14532,25 @@ ffmpeg -i INPUT -vf trim=duration=1
 
 @end itemize
 
+@section unpremultiply
+Apply alpha unpremultiply effect to input video stream using first plane
+of second stream as alpha.
+
+Both streams must have same dimensions and same pixel format.
+
+The filter accepts the following option:
+
+@table @option
+@item planes
+Set which planes will be processed, unprocessed planes will be copied.
+By default value 0xf, all planes will be processed.
+
+If the format has 1 or 2 components, then luma is bit 0.
+If the format has 3 or 4 components:
+for RGB formats bit 0 is green, bit 1 is blue and bit 2 is red;
+for YUV formats bit 0 is luma, bit 1 is chroma-U and bit 2 is chroma-V.
+If present, the alpha channel is always the last bit.
+@end table
 
 @anchor{unsharp}
 @section unsharp