GMT中翻转色度条的颜色
在使用GMT绘图时，比如同样是rainbow色度条，在水储量大小表示时，蓝色更能代表水量充足，而黄色是亏损；而如果是表示温度，暖色可以代表高温，冷色低温。因此在科研绘图中，我们需要翻转色度条。
下面我举一例：
比如是如下的情况，采用等效水高表示：如果需要翻转色度条，需要更改makecpt语句
makecpt -Cjet -T-0.6/0.6/0.05 >1.cpt【之前】
makecpt -Cjet -T-0.6/0.6/0.05 -I>1.cpt【翻转】
我们可以看到只需要在命令中加上 -I即可。
makecpt命令的使用说明：
makecpt [-A[+]<transparency>] [-C<cpt>|colors] [-D[i|o]] [-E<nlevels>] [-F[R|r|h|c][+c]] [-G<zlo>/<zhi>]
[-I[c][z]] [-L] [-M] [-N] [-Q[i|o]] [-T<z_min>/<z_max>[/<z_inc>[+n]] | -T<table> | -T<z1,z2,...zn>] [-V[<level>]] [-W[w]]
[-Z] [-bi[<ncol>][t][w][+L|B]] [-di<nodata>] [-i<cols>[+l][+s<scale>][+o<offset>][,...]]
[-ho[<nrecs>][+c][+d][+r<remark>][+t<title>]]
OPTIONS:
-A Set constant transparency for all colors; prepend + to also include back-, for-, and nan-colors [0]
-C Specify a colortable [Default is rainbow]:
[Notes: R=Default z-range, H=Hinge, C=colormodel]
---------------------------------------------------------------------------------------
abyss : Black/dark blue to lightblue for bathymetry [R=-8000/0, C=RGB]
bathy : Like abyss but via aquamarine at mid-depths [R=-8000/0, C=RGB]
categorical : Color table particularly suitable for categorical data [vRGB]
cool : Linear change from blue to magenta [C=RGB]
copper : Dark to light copper brown [C=RGB]
cubhelix : Intensity colormap via cube helix by Dave Green [C=RGB]
cyclic : Cyclic colormap, spans 360 degrees of hue [C=HSV]
dem1 : Digital Elevation Model (DEM) scale by Thomas Dewez [R=0/800, C=RGB]
dem2 : Digital Elevation Model (DEM) scale by Dewez/Wessel [R=0/4900, C=RGB]
dem3 : Digital Elevation Model (DEM) scale by Paul Wessel [R=0/6000, C=RGB]
dem4 : Digital Elevation Model (DEM) scale for Wikipedia figures [R=0/1500, C=RGB]
drywet : Goes from dry to wet colors [C=RGB]
earth : Colors for global bathymetry/topography relief [R=-11000/9000, H=0, C=RGB]
elevation : Washed-out colors for topography [R=0/7000, C=RGB]
etopo1 : Colormap used in the ETOPO1 global relief map [R=-11000/8500, H=0, C=RGB]
gebco : Colors for GEBCO bathymetric charts [R=-7000/0, C=RGB]
geo : Colors for global bathymetry/topography relief [R=-8000/8000, H=0, C=RGB]
globe : Colors for global bathymetry/topography relief [R=-10000/10000, H=0, C=RGB]
gray : Gray linear ramp from black to white [C=RGB]
haxby : Bill Haxby's color scheme for geoid & gravity [C=RGB]
hot : Black through red and yellow to white [C=RGB]
ibcso : The IBCSO bathymetry colors [R=-12000/0, C=RGB]
inferno : New colormap Option B from matplotlib [C=RGB]
jet : Dark to light blue, white, yellow and red [C=RGB]
magma : New colormap Option A from matplotlib [C=RGB]
nighttime : Colors for DMSP-OLS Nighttime Lights Time Series [C=HSV]
no_green : For those who hate green [H=0, C=RGB]
ocean : White-green-blue bathymetry scale [R=-8000/0, C=RGB]
paired : Qualitative color map with 6 pairs of colors [C=RGB]
panoply : Default colormap of Panoply [C=RGB]
plasma : New colormap Option C from matplotlib [C=RGB]
polar : Blue via white to red [H=0, C=RGB]
rainbow : Rainbow: magenta-blue-cyan-green-yellow-red [C=HSV]
red2green : Polar scale from red to green via white [H=0, C=RGB]
relief : Wessel/Martinez colors for topography [R=-8000/+8000, H=0, C=RGB]
seafloor : Purple-blue-white bathymetry scale [R=-6000/0, C=RGB]
sealand : Smith bathymetry/topography scale [R=-6000/+3000, H=0, C=HSV]
seis : R-O-Y-G-B seismic tomography colors [C=RGB]
split : Like polar, but via black instead of white [H=0, C=RGB]
terra : Colors for global bathymetry/topography relief [R=-7000/7000, H=0, C=RGB]
topo : Sandwell/Anderson colors for topography [R=-7000/+7000, H=0, C=HSV]
viridis : New colormap Option D from matplotlib [C=RGB]
world : Colors for global bathymetry/topography relief [R=-7000/7000, H=0, C=RGB]
wysiwyg : 20 well-separated RGB colors [C=RGB]
---------------------------------------------------------------------------------------
[For more, visit http://soliton.vm.bytemark.co.uk/pub/cpt-city/]
Alternatively, specify -Ccolor1,color2[,color3,...] to build a linear
continuous CPT from those colors automatically.
-D Set back- and foreground color to match the bottom/top limits
in the output CPT [Default uses color table]. append i to match the
bottom/top values in the input CPT.
-E Use <nlevels> equidistant color levels from zmin to zmax.
This option implies we read data from given command-line files [or stdin] to
determine data range (use -i to select a data column, else last column is used).
If <nlevels> is not set we use the number of color slices in the chosen CPT.
-F Select the color model for output (R for r/g/b or grayscale or colorname,
r for r/g/b only, h for h-s-v, c for c/m/y/k) [Default uses the input model]
append +c to output a discrete CPT in categorical CPT format.
-G Truncate incoming CPT to be limited to the z-range <zlo>/<zhi>.
To accept one of the incoming limits, set that limit to NaN.
-I Reverse sense of CPT in one or two ways:
-Ic Reverse sense of color table as well as back- and foreground color [Default].
-Iz Reverse sign of z-values in the color table (takes affect before -G, T are consulted).【此处便是帮助文档中提到的具体的使用】
-M Use GMT defaults to set back-, foreground, and NaN colors
[Default uses the settings in the color table].
-N Do not write back-, foreground, and NaN colors [Default will].
-Q Assign a logarithmic colortable [Default is linear].
-Qi: z-values are log10(z). Assign colors and write z [Default].
-Qo: z-values are z; take log10(z), assign colors and write z.
If -T<z_min/z_max/z_inc> is given, then z_inc must be 1, 2, or 3
(as in logarithmic annotations; see -B in psbasemap).
-T Give <z_min>/<z_max> to change the z-range for the colorscale in z-units.
append /<z_inc> to sample the cpt discretely instead, or append +n to <z_inc>
to let <z_inc> indicate the number of z-values to produce instead.
Alternatively, supply (1) a filename with custom z-values or
(2) a comma-separated list of custom z-values.
-V Change the verbosity level (currently v).
Choose among 6 levels; each level adds more messages:
q - Quiet, not even fatal error messages.
n - Normal verbosity: only error messages.
c - Also produce compatibility warnings [Default when no -V is used].
v - Verbose progress messages [Default when -V is used].
l - Long verbose progress messages.
d - Debugging messages.
-W Do not interpolate color palette. Alternatively, append w for a wrapped CPT.
-Z Create a continuous color palette [Default is discontinuous,
i.e., constant color intervals]. Without -T or when using -T<z_min>/<z_max> this
has no effect; the input palette table is used untouched with possible scaling.
-bi For binary input; [<n>]<type>[w][+L|B]; <type> = c|u|h|H|i|I|l|L|f|D.
Prepend <n> for the number of columns for each <type>.
-di Replace any <nodata> in input data with NaN.
-h[i][<n>][+c][+d][+r<remark>][+t<title>] Input/output file has [0] Header record(s) [OFF]
Optionally, append i for input only and/or number of header records [0].
-hi turns off the writing of all headers on output.
append +c to add header record with column information [none].
append +d to delete headers before adding new ones [Default will append headers].
append +r to add a <remark> comment to the output [none].
append +t to add a <title> comment to the output [none].
(these strings may contain \n to indicate line-breaks)
For binary files, <n> is considered to mean number of bytes.
-i Sets alternate input column order and optional transformations [Default reads all columns in order].
-^ (or -) Print short synopsis message.
-+ (or +) Print longer synopsis message.
-? (or no arguments) Print this usage message
(See gmt.conf man page for GMT default parameters).
【gmt小技巧@我是水怪的哥----2021-12-26】
