# [NTG-context] Colormanagement

Hans Hagen j.hagen at xs4all.nl
Sat Nov 10 17:24:29 CET 2018

```On 11/10/2018 2:34 PM, Jan U. Hasecke wrote:
> Am 09.11.18 um 17:20 schrieb luigi scarso:
>> I think you should use the best colorspace (<something>rgb )
>> and let the print shop do its job -- of course this means that you have
>> signed  their sample (hard proof) of your project.
>>
>
> I really tend to do this. I am currently exploring the color management
> system of ConTeXt together with a friend you is working as a color
> manager in print industry.
>
> And my first try was a failure. The cmyk values in the resulting pdf
> file (with color profile) differs from the values we calculated (using
> the same color profile in Gimp).
>
> But we have to investigate  a bit further, so don't panic. Maybe I the
> fault was mine.
>
> Is there a test case tex file we could use to test the color management?
there is no real 1-1 translation from rgb-cmyk .. in many programs that
do that there is some additional magic (i remember that photoshop also
applied the paper properties and that there was no roundtrip)

this is where color profiles come in

even viewers (like acrobat) can apply some magic so that the colors come
out different from what you expect

try this on screen and in print:

\startMPpage

path p ; p := fullcircle scaled 1cm ;

fill p shifted (0cm,1cm) withcolor (1,1,0) ;
fill p shifted (1cm,1cm) withcolor (0,0,1,0) ;
fill p shifted (0cm,0cm) withcolor (1/2,1/2,0) ;
fill p shifted (1cm,0cm) withcolor (0,0,1/2,0) ;

\stopMPpage

Hans

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