On 17-02-2020 15:39, Hans Hagen wrote:

On 2/17/2020 3:03 PM, Jan U. Hasecke wrote:

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Are there any plans to automate these steps into ConTeXt? That would enable us to work in RGB the whole time. Only when creating a print pdf we would specify a color profile and ConTeXt would do the rest by converting all rgb values to cmyk values due to the given color profile.

that would mean plugging some color transfer function into the rgb -> cmyk conversion that is already there (but i never had to deal with color transfer functions)

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As this seems very complex I fear that there are no plans to do this. not unless i know exactly what to do (or am forced to use it myself)

can't you use spotcolors? these are kind of standardized (say pantone)

As in print the default is CMYK, why not start there. The online might be RGB but all pdf viewers know how to deal with the convertion from CMYK to RGB by themselves. .F

On 17-02-2020 16:10, juh wrote:

At least, digital images are always RGB.

In my special case we started with a RGB corporate design as we are an online cooperative. Print comes later.

The thing is that in print the CMYK will result in a fixed well defined object: a physical print on paper. That is then the reference. The complete chain of getting the information into print is well defined. Compare that to the world of digital monitor viewing. None is well defined, every monitor and platform has its own unknown settings. How would you translate those into a printed document? So my point was that it might be more convenient to first create the publication for print, then let individual pdf browsers do their trick in their own environment rendering the CMYK into RGB or whatever... Unless it is fun to do both of course... .F

Am 2020-02-17 um 17:57 schrieb Jan U. Hasecke :

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.

✔︎

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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.

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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