behaviour of makecpt

[liming-he]

See below the output.

I expect to see different colours for Row #1 and R#2; however, Row #1 and Row #2 are in the same colour.

The first example is from: https://docs.juliahub.com/GMT/EoU0j/0.29.0/makecpt/#Discrete-versus-Continuous-CPT

Is this a bug, or did I misunderstand the example? Many thanks. -LH.

julia> makecpt(cmap=(:red,:green,:blue), range=[0,100,300,1000], no_bg=true)
Extract of a GMTcpt exposed as a GMTdataset for display. Colors converted to [0-255]
Model: rgb
Color depth: 24
3×9 GMTdataset{Float64, 2}
Row │ r1 g1 b1 r2 g2 b2 alpha z1 z2
│ Float64 Float64 Float64 Float64 Float64 Float64 Float64 Float64 Float64
─────┼─────────────────────────────────────────────────────────────────────────────────
1 │ 255.0 0.0 0.0 255.0 0.0 0.0 0.0 0.0 100.0
2 │ 255.0 0.0 0.0 255.0 0.0 0.0 0.0 100.0 300.0
3 │ 0.0 255.0 0.0 0.0 255.0 0.0 0.0 300.0 1000.0

julia> topo = makecpt(cmap=(:red, :blue, :green, :yellow), range= [0.0, 0.01, 0.05, 0.1, 0.2]) #make colorbar other options: color=:polar
Extract of a GMTcpt exposed as a GMTdataset for display. Colors converted to [0-255]
Model: rgb
Color depth: 24
4×9 GMTdataset{Float64, 2}
Row │ r1 g1 b1 r2 g2 b2 alpha z1 z2
│ Float64 Float64 Float64 Float64 Float64 Float64 Float64 Float64 Float64
─────┼─────────────────────────────────────────────────────────────────────────────────
1 │ 255.0 0.0 0.0 255.0 0.0 0.0 0.0 0.0 0.01
2 │ 255.0 0.0 0.0 255.0 0.0 0.0 0.0 0.01 0.05
3 │ 0.0 0.0 255.0 0.0 0.0 255.0 0.0 0.05 0.1
4 │ 255.0 255.0 0.0 255.0 255.0 0.0 0.0 0.1 0.2

[joa-quim]

Had a very quick look (need to go out) and yes, there seems to be some error. Try

C = makecpt(cmap=(:red,:green,:blue), range="0,100,300,1000", no_bg=true)
imshow(C)

Note that the GMT.jl location is not that anymore. Type @? makecpt to see the new docs.

(I'll come back when I find what the first form is not working well)

[liming-he]

Thanks for the quick response. It is something relating to the non-linear scale.

[joa-quim]

Indeed, the behavior depends on the numbers, which is not right. It really looks a bug upstream (GMT binary)

# good

julia> makecpt(cmap=(:red,:green,:blue), range=[0 100 200 450])
Extract of a GMTcpt exposed as a GMTdataset for display. Colors converted to [0-255]
Model: rgb
Color depth: 24
3×9 GMTdataset{Float64, 2}
 Row │      r1       g1       b1       r2       g2       b2    alpha       z1       z2
     │ Float64  Float64  Float64  Float64  Float64  Float64  Float64  Float64  Float64
─────┼─────────────────────────────────────────────────────────────────────────────────
   1 │   255.0      0.0      0.0    255.0      0.0      0.0      0.0      0.0    100.0
   2 │     0.0    255.0      0.0      0.0    255.0      0.0      0.0    100.0    200.0
   3 │     0.0      0.0    255.0      0.0      0.0    255.0      0.0    200.0    450.0

# broken

julia> makecpt(cmap=(:red,:green,:blue), range=[0 100 200 451])
Extract of a GMTcpt exposed as a GMTdataset for display. Colors converted to [0-255]
Model: rgb
Color depth: 24
3×9 GMTdataset{Float64, 2}
 Row │      r1       g1       b1       r2       g2       b2    alpha       z1       z2
     │ Float64  Float64  Float64  Float64  Float64  Float64  Float64  Float64  Float64
─────┼─────────────────────────────────────────────────────────────────────────────────
   1 │   255.0      0.0      0.0    255.0      0.0      0.0      0.0      0.0    100.0
   2 │   255.0      0.0      0.0    255.0      0.0      0.0      0.0    100.0    200.0
   3 │     0.0      0.0    255.0      0.0      0.0    255.0      0.0    200.0    451.0

[liming-he]

Thanks!

[joa-quim]

For reference, issue GenericMappingTools/gmt#7558

[liming-he]

Thanks for tracking the error.

[joa-quim]

Fixed in #1200

[liming-he]

thanks!