[cairo] Spot colors (and CMYK)

Kai-Uwe Behrmann ku.b at gmx.de
Thu Jan 21 07:10:21 PST 2010

Am 20.01.10, 19:17 -0500 schrieb James Cloos:
>>>>>> "Bill" == Bill Spitzak <spitzak at gmail.com> writes:
> Bill> I do not understand. What exactly do you think EVERY SINGLE PROGRAM IN
> Bill> THE WORLD does with those current CMYK "alternatives" when they draw
> Bill> them on the screen?
> Bill> I find it impossible to believe that any program does anything other
> Bill> than the simplistic conversion. Any "smarter" program will instead use
> Bill> the pantone color directly.
> Look at the XPDF or poppler src.  They follow adobe's lead in converting
> DeviceCMYK to DeviceRGB (aka sRGB).  The transform is straight forward,
> not too complex, but is not at all a simple r=m-1 kind of transform.
> Also, look for:
> /usr/share/ghostscript/${VERSION}/Resource/ColorSpace/DefaultCMYK
> and compare that against the TrivialCMYK in the same dir.  That does the
> same transform.
> The idea is to simulate the look of a typical office colour laser
> printing to typical office uncoated paper on an sRGB monitor when
> each is viewed in conditions.

Xpdf/poppler just at the beginning to support colour management, if the 
version you have seen has CM at all.

A proper way to simulate a output device on screen is to take the output 
devices ICC profile in account not some fixed formula.

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

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