Transparent Contor Color

Q&A
1

Hello,
I am working on a base map with contours, and I want to color the contours as a transparent. I have a cpt file for that.
Here’s the map before trying to color it:

image
image846×891 149 KB

I used the command: gmt grdimage contour.grd $REG $PROJ -Ccolors.cpt -t80 -O -K >> gmt.ps
I am trying to color only the range between 300 and 5000 for the map. However, after using the above command, the result is this:
image
image857×885 69.6 KB

Any thoughts? I want the color to be transparent and the black places to show the base map not black.

Thank you

2

I would say that it’s due to the background color in the CPT but without a reproducible (small) example you probably won’t get much more help.

3

What Joaquim said, an small code excerpt is easier…

Though, you have options. Have you tried the -L flag in grdcontour ?

4

I think that ex16 can help you ((16) Gridding of data, continued — GMT 6.6.0 documentation)

Check at the cpt here: gmtserver-admin/cache/ex_16.cpt at master · GenericMappingTools/gmtserver-admin · GitHub