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| author | Uoti Urpala <uau@symbol.nonexistent.invalid> | 2008-07-23 01:47:30 +0300 |
|---|---|---|
| committer | Uoti Urpala <uau@symbol.nonexistent.invalid> | 2008-07-23 02:05:55 +0300 |
| commit | 4dab4347f5d7bb3642a2c5918fc29855f8f62482 (patch) | |
| tree | 4f1f572dcd5cfee177658d28de3e1c3ce015dd65 /access_mpcontext.h | |
| parent | 2d4656e070697cebe8cb66568b3e8dd8919b5eed (diff) | |
| download | mpv-4dab4347f5d7bb3642a2c5918fc29855f8f62482.tar.bz2 mpv-4dab4347f5d7bb3642a2c5918fc29855f8f62482.tar.xz | |
vf_ass: Optimize alpha multiply
The effect of alpha blending was calculated as
color = orig_color * alpha / 255
where alpha and color range from 0 to 255.
Change this to
color = (orig_color * alpha + 255) / 256
where the "/ 256" can be expressed as a shift whereas the compiler
would probably generate a multiply+shift for the original "/ 255".
This formula gives a result that is too high by 1 for some inputs.
However it gives the exact result if alpha is 0 or 255 which is
probably the case where small errors would matter most.
Diffstat (limited to 'access_mpcontext.h')
0 files changed, 0 insertions, 0 deletions