Re: Any plans for an active color management?

[Henning Hraban Ramm <hraban@fiee.net>]

> Am 2020-02-17 um 17:57 schrieb Jan U. Hasecke <juh+ntg-context@mailbox.org>:
> 
> I contacted three print shops and they demand three different color
> profiles, one of them prints on "100 % recycling paper" with an uncoated
> profile. The other two use ISO Coated v2 300% and Coated Fogra 39.

Oh my, the sick state of my industry…
But ISO Coated and Coated FOGRA are quite similar.

> Being online shops I think they will complain if not the right profile
> is provided. But anyway.

They probably won’t recognize if you use any or no profile...

> 1. All my images should be profiled. I think I can do this in Gimp.

✔︎

>> For type and logos I still rely on (device dependend) CMYK colors and
>> my experience how they’ll come out in Euroscale printing. 
> Device depended means what?

Not profiled.

I.e. the actual resulting color depends on the device, if it’s only defined as RGB or CMYK values, those don’t define a location in L*a*b color space without a profile.

> I did this to convert our RGB corporate colors to device depended CMYK:
> 
> transicc -i sRGB.icc -o Fogra/Iso-whatever.icc

Never used lcms, sorry. Always wanted to try...

> But what shall I do with the logo? It is a RGB SVG.

AFAIK SVG uses sRGB per definitionem.
But I don’t know what happens on conversion.

I just checked:
You can set an output intent color profile in Inkscape’s document settings, and the reference ends up in the SVG (with an absolute path).
If I define colors in CMYK, they get safed only as (HTML-style) RGB colors, but if I re-open the file, CMYK color values are still the same. Don’t know how Inkscape does it.
The exported PDF (using cairo) is not profiled (DeviceRGB color space).

(Around 2004 there was a discussion about CMYK or profile based colors in SVG. I used the preliminary standard for color definitions in SVGs that were meant for exchange between a Flash based online ad designer and our EPS based newspaper workflow. I was in the position to force the programmers of that horrible Flash app to export something adhering to open standards… <evil grin> But then the SVG-color stuff got delayed and finally declined. I think there are profile based colors possible now, but Inkscape as one of the main SVG players doesn’t support them…)

> Do I understand you correctly that the best would be to ask someone with
> Indesign to convert it to CMYK with the above cited profile chain?

Mmm, no. Acrobat Pro can do proper profile conversions of graphics. Don’t know another tool.

> Or shall I tell the designer: These are the values I need as CMYK, just
> do it.

Exactly ;) Unfortunately they can’t really do that with Inkscape.

>> Colors that you define in TeX or Metapost are a different problem. I
>> *think* they should use the output intent as their profile. But I
>> don’t know if the intent option of \setupcolors and/or \setupbackend
>> really works this way. (My only means to check was Acrobat Pro 9, and
>> that won’t run on a current macOS any more.)
> 
> I do it like this:
> 
> \startmode[fogra39]
> \definecolor  [hs-logoblau]   [c=1.000, m=0.735, y=0.279, k=0.160]
> \definecolor  [hs-dunkelblau] [c=0.844, m=0.544, y=0.070, k=0.000]
> \definecolor  [hs-hellblau]   [c=0.468, m=0.220, y=0.086, k=0.002]
> \definecolor  [hs-orange]     [c=0.127, m=0.832, y=1.000, k=0.042]
> 
> \setupcolors[cmyk=yes,rgb=no,]

Try to set the same intent profile in \setupcolors. (It’s older than \setupbackend, and I actually don’t know what it does.)

> \setupbackend[
>   format=PDF/X-3:2003,
>   intent={Coated FOGRA39 (ISO 12647-2:2004)},
>   ]
> \stopmode

BTW: ConTeXt enforces some properties of the PDF/X standards, e.g. you don’t get transparencies with PDF/X-3. While InDesign would fake such effects (generating bitmaps), you just get plain colors with ConTeXt. That took me by surprise. *This* you can avoid with PDF/X-4, but I don’t know if that might cause different problems (e.g. printshop workflows that can’t handle it).

> I like your thought that all profiles are more or less the same.

No, that’s a misunderstanding. The several ISO/FOGRA Coated profiles *are* very close, as well as their Uncoated counterparts, but these groups are distinct.
If you let print on recyling/offset/copy paper, you need an Uncoated profile; if they use coated/silk/image… paper, you need an Coated profile. There are also different sets of spot colors for coated/uncoated paper.

> That would mean that my designer could convert our SVG logo and our SVG icons
> to Device-profiled CMYK-PDF and I am good.

Not device profiled, but device dependend, that means unprofiled. I’d expect unprofiled colors to use the default color space, and that would probably the right thing.

> Thanks for your help.

You’re welcome.

Best, Hraban


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