[CREATE] Linear light workflow

[Øyvind Kolås]

On Tue, Mar 27, 2012 at 5:35 PM, Andrew Chadwick <a.t.chadwick at gmail.com> wrote:
> How do (did) GIMP and Krita manage this for their native formats, OOI?

GIMP doesn't, yet. In the goat-invasion of GIMP gimp is even lying to
GEGL about the gamma by using the babl-format "RGBA u8" which is
linear 8bit data rather than "R'G'B'A u8" which is 2.2 gamma corrected
8bit data to get the expected legacy renderings. This will need to
change - as GEGL itself is preferring to do compositing in .. "RaGaBaA
float" linear premultiplied 32 bit floating point RGB.

The way that it will have to be handled is to add GEGL ops (perhaps
internal to GIMP) that does the compositing in gamma 2.2 rather than
linear. I hope that these layer modes will in the end only be used
when loading legacy XCF files and newer linear compositing will be
used when creating new images from scratch (the 2.2 gamma layer modes
could then be hidden.)

The need for having the legacy layer modes around will be required to
continue producing the same composited result (the same applies to
some of the odd HSV defined modes in GIMP.)

/Øyvind K.
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