[NTG-context] Which color model shall I use

Hans Hagen j.hagen at xs4all.nl
Mon Oct 1 10:08:38 CEST 2018


On 10/1/2018 9:23 AM, Jan U. Hasecke wrote:
> On 30.09.18 17:16, Henning Hraban Ramm wrote:
> 
>>
>> Hi juh,
>>
>> you can define colors in several color models at once; CMYK makes most sense for professional printing.
>>
>> e.g. \definecolor[CompanyBlue][r=0,g=0,b=1,c=1,m=1,y=0,k=0]
>>
>> and see https://wiki.contextgarden.net/Command/setupcolors
>> (I would activate rgb or cmyk colors via modes, if you produce different media)
> 
> I don't know how to enable this via modes.

\setupcolors[cmyk=yes,rgb=no] etc

>> CMYK colors in SVG are difficult (I needed them in 2005, nowadays there’s a hardly supported standard for icc profile based colors).
>> e.g. https://stackoverflow.com/questions/3405689/svg-image-with-cmyk-colours-is-it-possible
>> https://www.w3.org/TR/SVGColor12/#icc-colors
>>
>> Something about color profile handling in ConTeXt:
>> https://wiki.contextgarden.net/PDFX
>>
>> Now you must decide if you want to go the PDF/X-1a route (device dependent CYMK values) or PDF/X-3 (profiled colors).
> 
> How can I test, what colors are used in the resulting PDF? Currently I
> pick the colors with a tool in Gimp to see what colors come up.
> 
> If I look at the colors this way the RGB values of the included svg are
> always the original values defined by the file. All other values are not
> the values I defined in the ConTeXt files.
> 
> I think this is due to the cmyk conversion of my screen.
> 
> \setupbackend[
>   format=PDF/X-3,
>   intent=ISO Coated v2 (ECI),
> ]
> 
> I tried with this for example.
> 
> Anyway. Wouldn't it be better to produce a RGB-PDF and let the ripper of
> the print shop do the conversion? At least I can produce a RGB-PDF where
> all colors are defined in the same manner.
it depends ... 4 channel cmyk doesn't map entirely on 3 channel rgb and 
vise versa

Hans

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