I've been looking at the relevant babl/GEGL/GIMP code for enabling GIMP
to edit in color spaces other than sRGB. Here are two questions:
1. Code for retrieving colorant information from an ICC RGB working
space profile embedded in an image is already in
https://github.com/GNOME/gimp/blob/master/libgimpcolor/gimpcolorprofile.c
Can the following babl functions from
https://github.com/GNOME/babl/blob/master/babl/babl.h be used to send
RGB colorant information (a 3x3 matrix) from GIMP to various babl
functions that use Y and XYZ information?
/**
* babl_set_user_data: (skip)
*
* associate a data pointer with a format/model, this data can be
accessed and
* used from the conversion functions, encoding color profiles, palettes or
* similar with the data, perhaps this should be made internal API, not
* accesible at all from
*/
void babl_set_user_data (const Babl *babl, void *data);
/**
* babl_get_user_data: (skip)
*
* Get data set with babl_set_user_data
*/
void * babl_get_user_data (const Babl *babl);
2. Instead of full-blown support for editing in all RGB working spaces,
would it be easier and maybe even better to start with hard-coding into
babl/GEGL/GIMP an assortment of commonly-used RGB working space
chromaticities, including:
sRGB
Rec.2020
ACEScg
ACES
AdobeRGB
ProPhotoRGB
and then pass a numerical identifier from GIMP to babl as the user
switches from one image to another, so babl knows what chromaticities to
use? This option of course would require that the user make an ICC
profile conversion to one of the hard-coded RGB working spaces. But
given the many ICC RGB profiles floating around that are not
well-behaved and/or have odd TRCs, maybe this is the better option.
Though support for "random RGB chromaticities" would be nice to
eventually add in.
Best,
Elle
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