On Mon, Oct 6, 2014 at 6:57 PM, Elle Stone <ellestone@xxxxxxxxxxxxxxxxxxxx> wrote: > On 10/05/2014 12:49 PM, Øyvind Kolås wrote: > You've conceded that your architecture is broken to the point where you must > hack in fixes for multiply. That's the first of many such hacks to come: This is not the first such aspect of how pixel representation affects computation that operation developers must take into consideration for their operation (in which BablFormats they request). It is the same type of choice already existing with regard to linear/perceptual as well as pre-multiplied alpha or not, and should be dealt with in a similar way. I am going to try to describe the architecture of babl without mentioning color.. instead of doing color computations we will pretend to be doing temperature computations. Exactly how GEGL uses babl is not relevant for the discussion. Unfortunately enough - humans have many temperature scales, and they use different temperature scales for different purposes. To facilitate cooperation between scientists, engineers and others we have developed a convention of tagging numbers we use to refer to temperature with a unit qualifier, like thus: 37.7°C 100°F 310.9°K. That way, given a set of conversions formulas, it is possible to operate in the preferred unit. Some chemists need to do computations based on temperature relative to the _local_ boiling point of water. To facilitate this one can introduce a convention of local temperature; which could be 0.0 T at 0.0 C and 100.0 T when water boils at current altitude, that would might make these computations easier, this unit is the same as C some places on earth and different elsewhere. Being unchangeable units - like - C, K and F is the purpose for BablFormats existing, and the unit T is the proposed extension of our vocabulary for these recipies/chemistry formulas/whatisit that works differently at different heights. I understand you to propose using T everywhere; (or a set of new Ts; because in our case the differences between C and F are more important than in the real world, and mean alpha/linearity/precision). Or that interfaces at the edges of our system that are using C and F and working well with it should be discarded or reimplemented - because C and F will no longer mean what they meant when these systems were established. /pippin _______________________________________________ gegl-developer-list mailing list List address: gegl-developer-list@xxxxxxxxx List membership: https://mail.gnome.org/mailman/listinfo/gegl-developer-list
