How to change the coloured cpt file to gray coloured cpt

Q&A PyGMT Q&A
1

I am trying to make a gray color map using pygmt. While using cmap=‘dem1’ it gives me the nice coloured map with higher resolution.
Moreover while I am trying the cmap=‘gray’ it lost the resolution so i am trying to change dem1 to gray color.
However while i am changing the makecpt of dem1 as x=pygmt.makecpt(cmap=‘dem1’,series=’-1000/1000/0.1’,continuous=True) it doesnot give the gray coloured image

If anbody will suggest a better solution for the same, it will be very helpful.
My script is

fig = pygmt.Figure()
fig.basemap(region=region, projection=“M8c”, frame=[“Wsne”, “x1+lLatitude(°)”, “y1+lLongutide(°)”])
x=pygmt.makecpt(cmap=‘dem1’,series=’-1000/1000/0.1’,continuous=True)
topo_data = “@earth_relief_30s”
fig.grdimage(grid=topo_data,region=region,cmap=x,projection=‘M8c’,shading=False)

2

Hello @seis,

to write a colormap created with pygmt.makecpt to a file you have to use the output parameter (see also pygmt.makecpt — PyGMT):

# make colormap for elevation
pygmt.makecpt(
    cmap="grayC",
    series="0/2000/10",
    continuous=True,
    output="cpt_ele.cpt",
)

Something like x = pygmt.makecpt(...) does not work. Thus, your change of the cmap parameter does not affect the colormap used by pygmt.Figure.grdimage.

3

o i will try and let you know

4

Madam, It gives the map, however in the map some portion gets gray another portion get black, can you please suggets how to make it the whole map gray color.

5

Probably you have to adjust the range of your colormap using the series parameter ("min/max/step") in the way that it fits the range of your elevation grid.

Maybe you can complete your posted script by providing the values of region used for your map :wink:.