[cairo] Spot colors (and CMYK)

Andrea Canciani ranma42 at gmail.com
Thu Feb 18 10:57:08 PST 2010

On Thu, Feb 18, 2010 at 6:56 PM, Bill Spitzak <spitzak at gmail.com> wrote:
> Apple and Adobe provide a FIXED conversion from sRGB to the display.
> This is the REAL solution and is exactly what everybody wants. Please
> look, there are apis in Cocoa to draw images that do not provide a "cms"
I've been unable to find these APIs (looking only in not deprecated sections).
> but they WORK and you can actually adjust your screen to produce the
> correct color, and every program agrees! In the most recent versions
> they fixed it so OpenGL is also passed through this FIXED conversion and
> that has been a godsend, FINALLY we are getting matching images from all
> our software!
> Yes there are apis to provide a cms so they can concatenate it with
> their internal one. However this is the PROBLEM, not the solution. We
> certainly never use this, but from our experience with other cms
> libraries I can be pretty certain there are a million bugs with this
> concatenation so that the result never matches what happens if I convert
> to the fixed sRGB space and send that, and this means images do not match.
> Believe me I am very interested in emulating how Apple is doing things,
> and that I think your ideas are EXACTLY OPPOSITE this.
Actually all of the quartz surface/image creation functions have a
colorspace parameter.
They are quite similar to what Adrian Johnson came up with when trying
to add colorspace support to cairo (and tightly related to PDF
design). This seems the right way to follow and is what I'll probably
implement. I'll post the proposed extension to current API as soon as
Andrea Canciani
PS: I tried to get a few snapshot of my desktop with different color
profile settings. I found amazing how well color management is handled
by "Preview" (I used it to both grab and view the images). The images
were automatically created with the ICC profile currently set on the
screen (and it was attached to the image, too) and used as such (i.e.
displayed correctly, not ignoring it). I realize that most of this is
not done by Preview itself, but by Quartz and I think that the same
should happen in cairo.

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