[Gimp-developer] Applying 16 bit curves on import

[Martin Nordholts]

Edward Coffey wrote:
> Hi all,
>
> Since (if I understand correctly) the color adjustment tools in GIMP
> have been updated to use GEGL, would it be viable to introduce an
> optional 16 bit color-correction stage to the import of 16 bit images?

Hi!

Not without quite a bit of effort. The point of porting stuff to GEGL is
indeed to make such things possible, but in the current code the image
data is compressed to 8-bit per channel already in the loading-from-file
phase (at least for 16 bpc .pngs), i.e. before we have a chance to use
any colour adjustment tools on the data.

In order to support the above one would have to at least

1. Extend the plug-in API to deal with high bit-depth images
2. Adapt the core to store the high bit-depth data
3. Adapt the core to pass the high bit-depth data to the colour
adjustment tools.

The only thing you "get for free" is that the colour tools already do
their processing in 32-bit per channel linear light RGBA, so if you
manage to give them high bit-depth data they can handle that.

Note that in GIMP trunk the projection construction code, i.e. the code
that combines layers into a single image, is as good as ported to GEGL
too. Support for high bit-depth and non-destructive editing is in other
words closer than ever, but there's still a lot to do.

BR,
Martin