[Bf-committers] Color space and alpha issues

Troy Sobotka troy.sobotka at gmail.com
Sat Dec 17 04:40:13 CET 2011

On Dec 15, 2011 11:50 PM, "Bartek Skorupa" <bartekskorupa at bartekskorupa.com>
> Re wiki page: When explaining math behind mixing "Over" image with
> background (straight alpha) it should be: [(Over.RGB * Over.Alpha) +
> (Background.RGB * (1 - Over.Alpha))].
> Formula at the page is: [(Over.RGB * Over.Alpha) + Background.RGB].
> Shouldn't it be corrected?

Yes. It was my oopsie in a hasty attempt to illustrate that premultiplied
alpha actually changes the over operation. It allows for luminescent
additive pixels with an alpha of zero.

I will try to fix it from my phone.

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