Hi!
I've been playing with the Synfig blending methods to compare them with the
Cairo operators.
I started by coding a simple application that writes to png the different
examples that uses the cairo operators from here:
http://cairographics.org/operators/
Then I created the two same rectangles in Synfig and made an animation with
the all the blending modes.
I expected that the CAIRO_OPERATOR_OVER where directly the same than
Color::BLEND_COMPOSITE but it isn't!. When making gamma in Synfig Studio
and non selecting the color visually linear (in preferences) the source and
destiny colors are the same but the result color in the blended are is not
the same.
The reason is that gamma for targets is hard coded. It is hard coded
everywhere and although you select a different gamma in Synfig Studio it
still doing the gamma conversion all the time.
Mathematically I've checked that both operators give the same result but
when gamma scaling is involved everything changes.
On the other hand, when handling the Cairo render withing Synfig (not from
the small application I did) the result is also wrong but I do a (hard
coded again) operation to correct the gamma just before export to png (so
finally the result is the same than from Synfig).
All this story is to put on the desk that the gamma curse is an issue
absolutely needed to be fixed. It is really a nightmare to compare colors
form outside applications when Synfig is involved.
I know that it is not a trivial task but it would be great if someone else
starts to work on this and makes a plan to fix it. I'm looking forward to
fix it by myself but I don't want to divide my free time in more projects
than Cairo render that I'm involved now.
Cheers!
-G
--
Carlos
http://synfig.org
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