[cairo] Spot colors (and CMYK)
spitzak at gmail.com
Wed Jan 13 11:36:06 PST 2010
I certainly don't want to see a malloc/free pair just to set a color!
I think instead the apis can take an enumeration describing the "type"
of color followed by a pointer to the data. I would purposely not allow
any ability to get colors *from* Cairo so that the backend is free to
immediatly translate to device space (ie to 32 bit color) and not keep
the original color around.
Something like this:
cairo_set_source_color(cairo_t*, cairo_color_type_enum, float data);
I can't see any good way around having to cast the final pointer if the
data is not an array of floats.
Besides CMYK and spot colors I would like to see the ability to specify
the color as a 32-bit BGRA number, so that users can pull colors out of
the very same images they are telling Cairo to draw and guarantee they
are getting a matching color. Currently you have to "guess" what the
translation from float is and the end result is that whatever
rounding/etc Cairo does will have to be fixed and can never be changed
even if people decide it was wrong.
Adrian Johnson wrote:
> A starting point for an API proposal to support CMYK colors is the
> 1) Expose cairo_color_t as an opaque type. This will allow supporting
> various types of color without an explosion in the number of API
> functions every time a new type of color is added.
> cairo_color_t *
> cairo_color_reference (cairo_color_t *color);
> cairo_color_status (cairo_color_t *color);
> cairo_color_destroy (cairo_color_t *color);
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