gnuplot / Support Requests / #304 narrow a color palette

A portable, multi-platform, command-line driven graphing utility

#304 narrow a color palette

Status: open

Owner: nobody

Labels: None

Priority: 5

Updated: 2025-06-24

Created: 2025-06-19

Creator: Alexander Stangl

Private: No

Hey,
I would like to narrow down a colour palette to use only a certain color range.
For example for viridis, which goes from dark blue to turquoise to yellow. I would like to have my data only in turquoise to yellow.
Of course there's the obvious way of just redefining the palette.
Also possible: if my data ranges from 0-10, I could set the cb range from -10:10 and have the wanted effect, but then my colorbox would be from -10:10 as well (which would be sufficient to cover 0:10).
So, my question could also be asked as: is there a way to control the range shown in the colorbox and the range of the palette individually, or they both are exclusively controlled via the cb range?

Thanks,
Alex

Discussion

Ethan Merritt - 2025-06-19

set cbrange maps the entire palette onto some range of values. There is no single command that will map only a portion of the palette. You can, however, expand a portion of the existing palette to replace the whole thing, which would satisfy your starting example of using only the top half of the viridis palette:

set palette viridis set colormap new vtop do for [i=1:256] { vtop[i] = vtop[128 + i/2] } set palette colormap vtop set cbrange [0:10]

Does that help?
If you would like to refer to this comment somewhere else in this project, copy and paste the following link:

Alexander Stangl - 2025-06-24

Dear Ethan,
thanks a lot, that's what I was looking for!

Last edit: Alexander Stangl 2025-06-24

If you would like to refer to this comment somewhere else in this project, copy and paste the following link:

narrow a color palette

A portable, multi-platform, command-line driven graphing utility

Group

Searches

Help

#304 narrow a color palette

Discussion