Commit graph

4 commits

Author SHA1 Message Date
Thibault Saunier
806ff70590 compositor: Add support for crossfade blending
Crossfading is a bit more complex than just having two pads with the
right keyframes as the blending is not exactly the same.

The difference is in the way we compute the alpha channel, in the case
of crossfading, we have to compute an additive operation between
the destination and the source (factored by the alpha property of both
the input pad alpha property and the crossfading ratio) basically so
that the crossfade result of 2 opaque frames is also fully opaque at any
time in the crossfading process, avoid bleeding through the layer
blending.

Some rationnal can be found in https://phabricator.freedesktop.org/T7773.

https://bugzilla.gnome.org/show_bug.cgi?id=784827
2017-08-03 12:59:43 -04:00
Jan Schmidt
d5ca311a0d compositor: Revert most of previous patch.
The calculation doesn't produce the same results.
Keep just the change to divide alpha by 255 instead of 256,
for slightly better accuracy
2015-03-16 04:00:44 +11:00
Jan Schmidt
badc0438d6 compositor: Fix blending functions
Correctly calculate alpha in a few places by dividing by 255,
not 256.

Fix the argb and bgra blending functions to avoid an off-by-one
error in the calculations, so painting with alpha = 0xff doesn't
ever bleed through from behind
2015-03-16 00:33:23 +11:00
Mathieu Duponchelle
11fa711c34 compositor: Add a new compositor based on the new GstVideoAggregator base class
It is a replacement for videomixer with a similare API

Co-Authored by: Thibault Saunier <tsaunier@gnome.org>

https://bugzilla.gnome.org/show_bug.cgi?id=731919
2014-06-20 19:53:33 +02:00