NAME
gmt2rgb - Converting a grdfile, a raw, or a Sun rasterfile to r/g/b
grids
SYNOPSIS
gmt2rgb infile -Gtemplate [ -Ccptfile ] [ -F ] [
-Ix_inc[m|c][/y_inc[m|c]] ] [ -Llayer ] [ -Rwest/east/south/north[r] [
-V ]
DESCRIPTION
gmt2rgb reads one of three types of input files: (1) A Sun 8-, 24-, or
32-bit rasterfile; we the write out the red, green, and blue components
(0-255 range) to separate grid files. Since the rasterfile 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 grdfile; 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 rasterfile. Since raw rastefiles have
no header, you have to give the image dimensions via the -W option.
infile The (1) Sun rasterfile, (2) 2-D binary grdfile, or (3) raw
rasterfile to be converted.
-G Provide an output name template for the three output grids. The
template should be a regular gridfile 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 Will force pixel registration [Default is grid registration].
-I x_inc [and optionally y_inc] is the grid spacing. Append m to
indicate minutes or c to indicate seconds.
-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 wesn. The
two shorthands -Rg -Rd stand for global domain (0/360 or
-180/+180 in longitude respectively, with -90/+90 in latitude).
For calendar time coordinates you may either give relative time
(relative to the selected TIME_EPOCH and in the selected
TIME_UNIT; append t to -JX|x), or 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 as indicated (however, input/output
and plotting formats are flexible).
-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 -Ctopo.cpt -Ghawaii_grv_%c.grd
To output the red component from the Sun raster radiation.ras file, use
gmt2rgb radiation.ras -Lr -Gcomp_%c.grd
SEE ALSO
gmtdefaults(l), gmt(l), grdedit(l), grdimage(l), grdmath(l), grdview(l)
GMT4.0 1 Oct 2004 GMT2RGB(l)
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