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@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

 

_______________________________________________
Therion mailing list
Therion@speleo.sk
https://mailman.speleo.sk/listinfo/therion