[Therion] Plan gridline colour changes unpredictably

[Martin Sluka]

Printers are allway dependent on setup of colour management in its driver. Pro printers are dependent on setup of RIPs sending data to them. Not easy task. 

Martin S. 

Odesláno z iPhonu

11. 8. 2021 v 21:15, Bruce Mutton <bruce at tomo.co.nz>:

> Thanks Martin
> Highlights the dangers of absorbing a language by osmosis.  A false sense of understanding!
> I’ll try that out and see how it works.
>  
> Out of interest I went back over old maps to check the colour of my gridlines.  Until a few weeks ago I only ever used the default rgb colour model, and even now I only specify rgb, but occasionally force Therion to convert by specifying a cmyk colour model.  I found that I actually got a random section of the two gridline output colours over previous years.  My excuse for not picking it as a Therion behaviour is that I routinely use a number of pdf viewers and printers.  They all present line thicknesses and colours slightly differently. Especially Sumatra pdf compared to most others.
>  
> Bruce
>  
>  
> From: Therion <therion-bounces at speleo.sk> On Behalf Of Martin Budaj
> Sent: Wednesday, 11 August 2021 07:23
> To: List for Therion users <therion at speleo.sk>
> Subject: Re: [Therion] Plan gridline colour changes unpredictably
>  
> Hi,
>  
> 0.5white doesn't work in CMYK properly (it's equivalent to 0.5*(0,0,0,0) = (0,0,0,0) = white)
> 0.1black doesn't work in RGB (it's 0.1*(0,0,0) = (0,0,0) = black)
>  
> So your formula produces 50% gray in RGB and 10% gray in CMYK. No idea why you got 10% gray in some RGB setups, some test data would be needed.
>  
> To get 10% grey colour you need to use 0.1[white,black] which works in all RGB, CMYK and Grayscale.
>  
> Cheers
> Martin 
>  
>  
> On Tue, Aug 10, 2021 at 11:29 AM Bruce Mutton <bruce at tomo.co.nz> wrote:
> Curious
>  
> I have in my layout some metapost code to redefine the plan gridlines, used without apparent problem for perhaps 10 years.  It includes a colour specification…
>  
> withcolor 0.1black+0.5white;
>  
> Mostly they come out like this, very light grey.  This example is exported using colour-model cmyk, but most of the time using colour-model rgb it looks exactly the same, in my current project (only variables are colour map-fg, some map previews on or off and the colour model).
> <image002.jpg>
>  
> For some reason, in my current project, if I use colour-model rgb for a particular output variant, I get a much darker gridline, as below.  Other variants with rgb, the colour of the gridline matches the first example.
> <image004.png>
>  
> Any hints as to why the difference?
> I might have expected this to occur with the new cmyk colour model, but it does not.
> So far it has only happened with in a single specific case when using the rgb colour model.  I’ll watch for more cases…
> Bruce
>  
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