[Bf-committers] Color Unpremultiply

[gespertino at gmail.com]

2012/2/19 Matt Ebb <matt at mke3.net>

> > Apart from that, I wonder if it's really necessary to have that option
> > instead of just applying it whenever premultiplied alpha is selected and
> > the output file is gamma-corrected.
>
> Eh? I presume you're talking about the render option that does this at
> the end of the pipeline before saving imagery out of the
> renderer/compositor, and not the option per image that does this when
> loading the image, right?
>

I was talking about the render option, yes. I can't see that option in the
other end :)
I see I was wrong when I suggested that the option should be removed. It
has to be there, but as I mentioned in my previous message, I think it
would make more sense if that option is in the composite node and not in
the rendering panel.
Maybe I came to that (wrong) idea because I associated inconsciously the
rendering setting with the output from seeing that option there. :-p


>
> The Sky/Premul/Straight options are purely blender internal renderer
> things, they don't have any bearing on what comes out of the
> compositor. You can un-premultiply a transparent image in the
> compositor and pipe it straight to the output if you like, and while
> it will look bad in the viewer, it is a valid thing to do if you
> really want to. In this case, you don't want another divide before
> colour space conversion and need the option, no matter what
> sky/premul/straight option is set for BI.
>

Yes, I know. I do divide premultiplied composites when I need to save
proper PNGs out from blender composites, so I can see what you mean.