[cairo] Subtractive API, part 1

Chris Murphy lists at colorremedies.com
Tue Feb 2 22:41:53 PST 2010

On Feb 2, 2010, at 4:19 PM, ecir hana wrote:

> On Sun, Jan 31, 2010 at 6:38 AM, Jon Cruz <jon at joncruz.org> wrote:
>> But, yes, spot colors *can* have ICC profiles.
> I'm thinking about this a since you posted it and I have to be honest
> with you - I never heard of ICC profiles for spot colors. Where can I
> read about it in more detail? Where can I can them? (even for
> DeviceN?)


Find and download the current 4.2 spec. You'll find it referred to as the "named colour class" profile. It contains the name of the spot color, a PCS (either XYZ or L*a*b*) value, and an optional output device specific value (such as for a particular press or proofing condition, could be RGB or CMYK, etc.)

These are not used for making color separations, but just for dealing with spot color solids.

output device class profiles support up to 15 channels in the ICC 4.2 spec, so you could have CMYK+4 spots if you wish, as a single output device class profile. In that case the "data colour space" signature is '8CLR" rather than "CMYK" or "RGB". If you have a four color, non-CMYK, color space, the signature is "4CLR", and so on. Any xCLR color space based output device class profile must also have a colorantTableTag which defines the channel both by a unique name and either XYZ or L*a*b* values.

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

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