[Bf-committers] Color pipeline todo: alpha

[Brecht Van Lommel]

Hi,

I updated an old wiki page that I wrote before the new color
management system was added, removing stuff that was already
implemented. It shows some issues that will need to be resolved.
http://wiki.blender.org/index.php/Dev:Source/Image/Color

Premul for float and key for byte images could work. It would be a bit
strange for painting, rendering, sequencer, where you'll get different
behaviour depending on float/byte, though only in the cases where the
image has areas with zero alpha. For the implementation it's a clear
rule though.

Brecht.

On Thu, Dec 20, 2012 at 6:17 PM, Ton Roosendaal <ton at blender.org> wrote:
> Hi all,
>
> Sergey will start soon on finishing one of the color management issues in Blender: alpha!
>
> Proposed is the following:
>
> - For render & composite we use linear color float buffers. These will use premul alpha only. (Nothing changes)
> - When such float buffers get converted to display graphics (typically 24 bits rgb): default will become straight alpha.
>
> This will solve issues using alpha-over for byte buffers. Straight alpha graphics is also common for painting programs (in Blender too). And it'll solve our long outstanding PNG conflict ;)
>
> Saving out byte buffers with premul can stay as option - I think. We can check on the file format spec for it.
>
> All corner cases for this change will have to be further evaluated. Just so people know the svn version of Blender might need some testing the next days.
>
> Feedback welcome too! Maybe there's a better idea?
>
> -Ton-
>
> ------------------------------------------------------------------------
> Ton Roosendaal  Blender Foundation   ton at blender.org    www.blender.org
> Blender Institute   Entrepotdok 57A  1018AD Amsterdam   The Netherlands
>
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