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Re: lab color emitted from quartz pdf context edward m taffel Thu Feb 02 22:02:44 2012

hello chris & list,

i’m now attempting to integrate claudio’s workaround, & on the D65 note: a 
leading color library supplies lab coordinates w/ the specification

"CIE-L*a*b*, D65, 2∞"
.

i expect this should affect creation of a lab space intended for use in 
creating lab color alternates—any thoughts?

thanks,
edward


On Dec 15, 2011, at 8:41 PM, Chris Murphy wrote:

> 
> 
> On Dec 15, 2011, at 6:34 PM, Olaf Drümmer wrote:
> 
>> If you define a Lab color space directly in PDF syntax, there is no need (or 
>> actually: no way) to indicate the range for L (as it is assumed to always be 
>> 0..100 anyway). a and b are theoretically open ended and thus need to be 
>> constrained (though usually that's -128...127 anyway). Excerpt from PDF 1.7 
>> as defined in ISO 32000-1:
>> 
>> 
>> [ 
>> /Lab
>> <<   
>>      /WhitePoint     [ 0.9505        1.0000  1.0890 ]
>>      /Range [-128 127 -128 127]
>> >>
>> ]
> 
> 
> Those are XYZs for a D65 white point. I'm unaware of any graphic arts or 
> photographic usage of a D65 Lab.
> 
> 
> Chris
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