[cairo] Subtractive API, part 0

[Chris Murphy]

On Jan 28, 2010, at 9:00 AM, ecir hana wrote:

> On Thu, Jan 28, 2010 at 1:09 PM, Arjen Nienhuis <a.g.nienhuis at gmail.com> wrote:
> 
> Thanks for the feedback!
> 
>> Your proposal assumes that its possible to do simple calculations on
>> CMYK values. It's not.
> 
> It is. Because of two things:
> - 90% black means that the raster simulating such color is comprised
> of dots covering 90% of surface area. The fact, that the ink gets
> soaked into the paper and the dots grow a bit ("dot gain") is
> completely unrelated problem.
> - it's just matter of definition: if I want half cmyk(0, 0, 1, 1) I
> really mean cmyk(0, 0, 0.5, 0.5). If I want half gray, I mean
> gray(0.5). How else do you what to say "half magenta" if not
> magenta(0.5)?

I am hopeful that there will be a day when people understand that "half magenta" is not a color. At best it is a rudimentary control signal to output somewhere between 25% and 75% of a colorant better referred to as "not quite bubble gum pink, brand unknown".

If you don't care about getting radically different colors when defining them in such a vague manner as "1/2 magenta" then fine. But at that point it seems rather pointless to have such a lack of control.

Chris Murphy
Color Remedies (TM)
New York, NY
----------------------------------------------------------------------
Co-author "Real World Color Management, 2nd Ed"