grd2rgb - Write r/g/b grid files from a grid file, a raw RGB file,
or SUN rasterfile
grd2rgb infile -Gtemplate [
-Ccpt ] [
-Ixinc[m|s][/yinc[m|s]] ] [
-Llayer ]
-Rregion
-V[level] [
-Wwidth/height[/n_bytes] ] [ -r ]
Note: No space is allowed between the option flag and the
associated arguments.
grd2rgb 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, -I, -r 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. 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.
- -Gtemplate
- 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.
- -Ccpt
- name of the color palette table (for 2-D binary input grid only).
- -Ixinc[unit][+e|n][/yinc[unit][+e|n]]
- 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 s to
indicate arc seconds. If one of the units e, f, k,
M, n or u is appended instead, the increment is
assumed to be given in meter, foot, km, Mile, nautical mile or US survey
foot, respectively, and will be converted to the equivalent degrees
longitude at the middle latitude of the region (the conversion depends on
PROJ_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 +e 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 +n 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 App-file-formats for details. Note: if
-Rgrdfile is used then the grid spacing has already been
initialized; use -I to override the values.
- -Llayer
- Output only the specified layer (r, g, or b). [Default outputs all 3
layers].
- -Wwidth/height[/n_bytes]
- 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.
- -^ or just -
- Print a short message about the syntax of the command, then exits (NOTE:
on Windows just use -).
- -+ or just +
- Print an extensive usage (help) message, including the explanation of any
module-specific option (but not the GMT common options), then exits.
- -? or no arguments
- Print a complete usage (help) message, including the explanation of all
options, then exits.
To use the color palette topo.cpt to create r, g, b component
grids from hawaii_grv.nc file, use
gmt grd2rgb hawaii_grv.nc -Ctopo.cpt -Ghawaii_grv_%c.nc
To output the red component from the Sun raster radiation.ras
file, use
gmt grd2rgb radiation.ras -Lr -Gcomp_%c.nc
gmt, gmt.conf, grdedit, grdimage, grdmath , grdview
2019, P. Wessel, W. H. F. Smith, R. Scharroo, J. Luis, and F.
Wobbe