[NTG-context] Which color model shall I use

Henning Hraban Ramm texml at fiee.net
Mon Oct 1 10:11:16 CEST 2018


Am 2018-10-01 um 09:23 schrieb Jan U. Hasecke <juh+ntg-context at mailbox.org>:

> 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.

\startnotmode[print]
\setupcolors[cmyk=no,rgb=yes]
\stopnotmode

\startmode[print]
\setupcolors[cmyk=yes,rgb=no]
\stopmode

>> 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.

Can Gimp check the colors in the PDF? (I don’t think so.)

I know no other tool for that than Acrobat Pro, but there probably are one or two others; don’t know if there are *free and usable* tools to check on colors/profiles in PDFs...

> 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.

If you can ensure all RGB colors are tagged with the same profiles then it should work, as long as you only care about *same* colors and not (CMYK-defined) *specific* colors...

Do your SVGs declare their RGB color space?

Color management *is* complicated.

Greetlings, Hraban
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