GMT2RGB(1) Generic Mapping Tools GMT2RGB(1)NAMEgmt2rgb - Converting a grid file, a raw, or a Sun raster file to r/g/b
grids
SYNOPSISgmt2rgb infile -Gtemplate [ -Ccptfile ] [ -F ] [
-Ixinc[m|c][/yinc[m|c]] ] [ -Llayer ] [ -Rxmin/xmax/ymin/ymax[r] ] [ -V
] [ -Wwidth/height[/n_bytes] ]
DESCRIPTIONgmt2rgb reads one of three types of input files: (1) A Sun 8-, 24-, or
32-bit raster file; we the write out the red, green, and blue compo‐
nents (0-255 range) to separate grid files. Since the raster file
header is limited you may use the -R, -F, -I options to set a complete
header record [Default is simply based on the number of rows and col‐
umns]. (2) A binary 2-D grid file; we then convert the z-values to red,
green, blue via the provided cpt file. Optionally, only write out one
of the r, g, b, layers. (3) A RGB or RGBA raw raster file. Since raw
rasterfiles have no header, you have to give the image dimensions via
the -W option.
infile The (1) Sun raster file, (2) 2-D binary grid file, or (3) raw
raster file to be converted.
-G Provide an output name template for the three output grids. The
template should be a regular grid file name except it must con‐
tain the string %c which on output will be replaced by r, g, or
b.
OPTIONS-C name of the color palette table (for 2-D binary input grid
only).
-F Force pixel node registration [Default is gridline registra‐
tion]. (Node registrations are defined in GMT Cookbook Appendix
B on grid file formats.)
-I x_inc [and optionally y_inc] is the grid spacing. Optionally,
append a suffix modifier. Geographical (degrees) coordinates:
Append m to indicate arc minutes or c to indicate arc seconds.
If one of the units e, k, i, or n is appended instead, the
increment is assumed to be given in meter, km, miles, or nauti‐
cal miles, respectively, and will be converted to the equivalent
degrees longitude at the middle latitude of the region (the con‐
version depends on ELLIPSOID). If /y_inc is given but set to 0
it will be reset equal to x_inc; otherwise it will be converted
to degrees latitude. All coordinates: If = is appended then the
corresponding max x (east) or y (north) may be slightly adjusted
to fit exactly the given increment [by default the increment may
be adjusted slightly to fit the given domain]. Finally, instead
of giving an increment you may specify the number of nodes
desired by appending + to the supplied integer argument; the
increment is then recalculated from the number of nodes and the
domain. The resulting increment value depends on whether you
have selected a gridline-registered or pixel-registered grid;
see Appendix B for details. Note: if -Rgrdfile is used then
grid spacing has already been initialized; use -I to override
the values.
-L Output only the specified layer (r, g, or b). [Default outputs
all 3 layers].
-R xmin, xmax, ymin, and ymax specify the Region of interest. For
geographic regions, these limits correspond to west, east,
south, and north and you may specify them in decimal degrees or
in [+-]dd:mm[:ss.xxx][W|E|S|N] format. Append r if lower left
and upper right map coordinates are given instead of w/e/s/n.
The two shorthands -Rg and -Rd stand for global domain (0/360
and -180/+180 in longitude respectively, with -90/+90 in lati‐
tude). Alternatively, specify the name of an existing grid file
and the -R settings (and grid spacing, if applicable) are copied
from the grid. For calendar time coordinates you may either
give (a) relative time (relative to the selected TIME_EPOCH and
in the selected TIME_UNIT; append t to -JX|x), or (b) absolute
time of the form [date]T[clock] (append T to -JX|x). At least
one of date and clock must be present; the T is always required.
The date string must be of the form [-]yyyy[-mm[-dd]] (Gregorian
calendar) or yyyy[-Www[-d]] (ISO week calendar), while the clock
string must be of the form hh:mm:ss[.xxx]. The use of delim‐
iters and their type and positions must be exactly as indicated
(however, input, output and plot formats are customizable; see
gmtdefaults).
-V Selects verbose mode, which will send progress reports to stderr
[Default runs "silently"].
-W Sets the size of the raw raster file. By default an RGB file
(which has 3 bytes/pixel) is assumed. For RGBA files use
n_bytes = 4. Use -W for guessing the image size of a RGB raw
file, and -W=/=/4 if the raw image is of the RGBA type. Notice
that this might be a bit slow because the guessing algorithm
makes uses of FFTs.
EXAMPLES
To use the color palette topo.cpt to create r, g, b component grids
from hawaii_grv.grd file, use
gmt2rgb hawaii_grv.grd -C topo.cpt -G hawaii_grv_%c.grd
To output the red component from the Sun raster radiation.ras file, use
gmt2rgb radiation.ras -L r -G comp_%c.grd
SEE ALSOgmtdefaults(1), GMT(1), grdedit(1), grdimage(1), grdmath(1), grdview(1)GMT 4.5.14 1 Nov 2015 GMT2RGB(1)
