[Bf-committers] Color space and alpha issues
francoistarlier at gmail.com
Fri Dec 16 16:25:01 CET 2011
that actually depend on how premult is implemented
2011/12/16 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?
> In my opinion it should be as follows:
> "over" image mixed with "normal" blending mode, or "mix" blending mode:
> [(Over.RGB * Over.Alpha) + (Background.RGB * (1 - Over.Alpha))]
> "over" image mixed with "Add" blending mode:
> [((Over.RGB + Background.RGB) * Over.Alpha) + (Background.RGB * (1 -
> "over" image mixed with "Multiply" blending mode:
> [((Over.RGB * Background.RGB) * Over.Alpha) + (Background.RGB * (1 -
> Other blending modes - accordingly to their math.
> Bartek Skorupa
> On 2011-12-15, at 15:31, Brecht Van Lommel wrote:
> > Hi,
> > Color management and alpha issues are a recurring topic, I've written
> > a wiki page explaining issues with the current code and what I think
> > should be done to solve them:
> > http://wiki.blender.org/index.php/Dev:Source/Image/Color
> > You might notice I'm not really mentioning OIIO/OCIO. It's a nice
> > project to integrate those, but it doesn't solve current issues and is
> > fairly orthogonal to the proposed changes.
> > I might not have time to tackle this for 2.62, but it doesn't
> > necessarily need to be done all in one big change. Feedback welcome,
> > about what you think should be done different, and which alpha format
> > convention should be used?
> > Thanks,
> > Brecht.
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