ctx supports grayscale, RGB and CMYK color models, all of which can be used and
freely mixed while drawing. Conversion to the device/compositing representation
is done during rasterization / rendering; at this point conversion between ICC
matrix profiles for RGB spaces is currently supported when babl
built in; making a hard-coded set of primaries known to match the specific
display used - without babl - would be nice for microcontroller use.
The default RGB color space for both device and user is sRGB. Thus code
from elsewhere specifying sRGB colors will work as expected. By adding
an RGB matrix display profile in /tmp/ctx.icc the SDL,DRM and fbdev backends
use the display space instead of sRGB for compositing.
TODO: manage conversions between CMYK and RGB