Re: [Gimp-developer] [Gegl-developer] babl roadmap

Am Mittwoch, 15. Oktober 2014, 15:37:01 schrieb Elle Stone:


The guiding principle should be that except in these carefully bracketed
and clearly identified cases, the *user* controls the RGB working space,
and all RGB editing operations should use the user's chosen primaries.

It seems this is the central point. The choice of bablRGB (or linear sRGB or 
linear Rec709) is merely an implementation detail and only works as the base 
transformation matrices are calculated on. Think of it as bablXYZ. It's the 
common ground babl does its color transformations on, just like ICC uses XYZ. 
This however is not the working space used in the gegl tree and therefore in 
GIMP. Just as applications using ICC internally don't work on XYZ data.

The reason why babl uses bablRGB instead of XYZ is just so that the common 
case of using sRGB data that is coming from the outside world (pippin gave the 
example of text rendered by cairo) can be used directly and doesn't need a 
conversion step. Code making use of the babl functions is free to keep every 
imported buffer in its native color space (probably linearized) and the system 
will make sure that the data is treated the right way when a conversion is 
required (for example when merging layers -- which format would win is 
probably a point to be discussed later).

At least that's how I understood the situation.

Kind regards,
Elle Stone


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