BLEND_ALPHA_OVER deprecation comment: "multiply alpha" ?

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Sylvain Leroux
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Joined: Fri Aug 19, 2016 8:09 am

BLEND_ALPHA_OVER deprecation comment: "multiply alpha" ?

Postby Sylvain Leroux » Sun Feb 26, 2017 4:23 pm

I was planning to develop a new blending method for my own needs -- very similar to the MULTIPLY blend mode, but setting alpha to [tt]A.alpha*B.alpha[/tt].

a
But by looking at the code I saw that:

https://github.com/s-leroux/synfig/blob ... lor.h#L294

Code: Select all

      BLEND_ALPHA_OVER=19,      //!< \deprecated multiply alphas and then straight blends using the amount


This feels like referring to something similar to what I had in mind. But -- as a SynfigStudio 1.0.2 user -- I don't understand exactly what this comment is talking about.

Any clue or pointer would be welcome;)
Synfig Studio 1.0.2 on Linux Debian Stretch/Sid

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caryoscelus
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Re: BLEND_ALPHA_OVER deprecation comment: "multiply alpha" ?

Postby caryoscelus » Sun Feb 26, 2017 5:23 pm

I'm not sure why it's deprecated and the comment seems to be wrong: you can try Alpha Over blending method and it clearly does something else. It seems to be subtracting alpha or something similar.

Sylvain Leroux
Posts: 20
Joined: Fri Aug 19, 2016 8:09 am

Re: BLEND_ALPHA_OVER deprecation comment: "multiply alpha" ?

Postby Sylvain Leroux » Sun Feb 26, 2017 5:28 pm

Yeah, after having dig a little bit deeper into the code, that comment still seems very puzzling. I don't see anything close to what ALPHA_OVER is supposed to do.

Lets assume for now the comments is wrong ;)
Synfig Studio 1.0.2 on Linux Debian Stretch/Sid


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