Re: System for choosing RGB or CMYK elements

Am 26.05.2026 um 18:24 schrieb Jan Ulrich Hasecke via ntg-context:
> Dear all,
> 
> my print shop just rejected my last context created pdf job because some 
> objects where rgb and some cmyk. For many good (or bad) reasons for too 
> long I delayed my plan to establish a system for choosing the right 
> elements according to the selected mode.
> 
> In short I want that context chooses cmyk elements when I use the 
> mode=isocoated for example, and when I use no mode or mode=web it shall 
> use rgb elements.
> 
> We have a lot of SVG graphics which are of course in rgb.
> I learned that I can convert these svg files via Scribus to cmyk pdf 
> files. This is just tedious work, but I guess unavoidable.
> 
> So I will end up with lots of files named filename.svg (RGB) for web 
> pdfs and filename.pdf (CMYK) for print pdfs.
> 
> I think  of using \setupexternalfigures inside startstopmode[isocoated] 
> to restrict method to pdf or something like this.
> 
> Is this feasible?
> 
> Or is it better to create files with a naming scheme that hints to the 
> color space like cow-rgb.pdf and cow-cmyk.pdf and use the right file 
> explicitly in the context file? I don't like this idea.
> 
> I know that I also must have a good solution for raster images.
> 
> What do you think? How do you solve this challenge?


You can try the svg to metapost conversion from context in combination 
with the rgb to cmyk color conversion.

The attached example shows a few ways how you can do the image format 
conversion in a document.

Wolfgang

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\setupcolors[rgb=no]

\starttext

% method 1

\startmode[a]

\externalfigure[49.svg][conversion=mp]
\externalfigure[50.svg][conversion=mp]

\stopmode

% method 2

\startmode[b]

\defineexternalfigure[svgtomp][conversion=mp]

\externalfigure[49.svg][svgtomp]
\externalfigure[50.svg][svgtomp]

\stopmode

% method 3

\startmode[c]

\useexternalfigure[49.svg][49.svg][conversion=mp]
\useexternalfigure[50.svg][50.svg][conversion=mp]

\externalfigure[49.svg]
\externalfigure[50.svg]

\stopmode

\stoptext