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GMT2RGB(1) Generic Mapping Tools GMT2RGB(1)
NAME
gmt2rgb - Converting a grid file, a raw, or a Sun raster file to r/g/b
grids
SYNOPSIS
gmt2rgb infile -Gtemplate [ -Ccptfile ] [ -F ] [
-Ixinc[m|c][/yinc[m|c]] ] [ -Llayer ] [ -Rxmin/xmax/ymin/ymax[r] ] [ -V
] [ -Wwidth/height[/n_bytes] ]
DESCRIPTION
gmt2rgb 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
components (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
columns]. (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
contain 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
registration]. (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
nautical miles, respectively, and will be converted to the
equivalent degrees longitude at the middle latitude of the
region (the conversion 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
latitude). 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 delimiters 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 ALSO
gmtdefaults(1), GMT(1), grdedit(1), grdimage(1), grdmath(1), grdview(1)
GMT 4.5.14 1 Nov 2015 GMT2RGB(1)