[cairo] Subtractive API, part 0

[Kai-Uwe Behrmann]

Am 28.01.10, 13:09 +0100 schrieb Arjen Nienhuis:
> cairo_set_source_icc_color(cairo_t *cr, float srgb_fallback_r, float
> srgb_fallback_g, float srgb_fallback_b, cairo_profile_t *profile,
> <array of float>)

It remembers me how named colours are used in Oyranos. However some 
questions remain open with Cairo not doing ICC style colour conversions:

* What is about images? really multiplying memory usage?
* What is with the compositing colour space? Non selectable?


An other idea slightly in this direction is to pass a real colour object 
to Cairo.

typedef struct {
   float srgba_fallback[4];   /**< gamma 2.2? */

#ifdef DO_IT_BETTER
   /** zero terminated list of data blobs, not necessarily text
    *  e.g. can contain spot colour names, reflectance ...
    */
   char ** properties;
   int * properties_len;      /**< length per properties element */
   int * properties_type;     /**< enum? define? mask? */
#endif

   cairo_profile_t * profile;
   float native_color[];
} cairo_color_t;

cairo_set_source_icc_color(cairo_t *cr, cairo_color_t * color);

A sRGB fallback is in place, even though from a design point of view 
CIE*XYZ would be much clearer.
One object means fewer typing.
Reuseable cairo_color_t objects.

Completely sticking to sRGB would be somehow weak. As a means to get the 
CM ball rolling it might fit its purpouse.


kind regards
Kai-Uwe Behrmann
-- 
developing for colour management 
www.behrmann.name + www.oyranos.org