[FFmpeg-devel] [PATCH] avfilter/vf_overlay: fix alpha blending for planar formats with a transparent background

[Michael Niedermayer]

On Fri, Aug 04, 2017 at 10:23:55AM +0200, Marton Balint wrote:
> When the background had an alpha channel, the old code in blend_plane
> calculated premultiplied alpha from the destination plane colors instead of the
> destination alpha.
> 
> Also the calculation of the output alpha should only happen after the color
> planes are already finished.
> 
> Fixes output of:
> ffplay -f lavfi "testsrc2=alpha=32[a];color=black[b];[b][a]overlay[out0]"

if it is easy, please add a fate test when / after you push this

thx

[...]
-- 
Michael     GnuPG fingerprint: 9FF2128B147EF6730BADF133611EC787040B0FAB

The misfortune of the wise is better than the prosperity of the fool.
-- Epicurus
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