[Therion] Plan gridline colour changes unpredictably

[Martin Budaj]

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).
>
>
>
> 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.
>
>
>
> 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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