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.TH "GRD2RGB" "1gmt" "Jan 10, 2019" "5.4.5" "GMT"
.SH NAME
grd2rgb \- Write r/g/b grid files from a grid file, a raw RGB file, or SUN rasterfile
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.SH SYNOPSIS
.sp
\fBgrd2rgb\fP \fIinfile\fP  \fB\-G\fP\fItemplate\fP
[  \fB\-C\fP\fIcpt\fP ] [
 \fB\-I\fP\fIxinc\fP[\fBm\fP|\fBs\fP][/\fIyinc\fP[\fBm\fP|\fBs\fP]] ]
[  \fB\-L\fP\fIlayer\fP ]
 \fB\-R\fP\fIregion\fP
 \fB\-V\fP[\fIlevel\fP]
[  \fB\-W\fP\fIwidth\fP/\fIheight\fP[/\fIn_bytes\fP] ]
[ \fB\-r\fP ]
.sp
\fBNote:\fP No space is allowed between the option flag and the associated arguments.
.SH DESCRIPTION
.sp
\fBgrd2rgb\fP 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 \fB\-R\fP, \fB\-I\fP, \fB\-r\fP 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 \fB\-W\fP option.
.SH REQUIRED ARGUMENTS
.INDENT 0.0
.TP
.B \fIinfile\fP
The (1) Sun raster file, (2) 2\-D binary grid file, or (3) raw raster file to be converted.
.TP
\fB\-G\fP\fItemplate\fP
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.
.UNINDENT
.SH OPTIONAL ARGUMENTS
.INDENT 0.0
.TP
\fB\-C\fP\fIcpt\fP
name of the color palette table (for 2\-D binary input grid only).
.UNINDENT
.INDENT 0.0
.TP
\fB\-I\fP\fIxinc\fP[\fIunit\fP][\fB+e\fP|\fBn\fP][/\fIyinc\fP[\fIunit\fP][\fB+e\fP|\fBn\fP]]
\fIx_inc\fP [and optionally \fIy_inc\fP] is the grid spacing. Optionally,
append a suffix modifier. \fBGeographical (degrees) coordinates\fP: Append
\fBm\fP to indicate arc minutes or \fBs\fP to indicate arc seconds. If one
of the units \fBe\fP, \fBf\fP, \fBk\fP, \fBM\fP, \fBn\fP or \fBu\fP 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 \fIy_inc\fP is given
but set to 0 it will be reset equal to \fIx_inc\fP; otherwise it will be
converted to degrees latitude. \fBAll coordinates\fP: If \fB+e\fP is appended
then the corresponding max \fIx\fP (\fIeast\fP) or \fIy\fP (\fInorth\fP) 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 \fInumber of nodes\fP desired by
appending \fB+n\fP 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 \fB\-R\fP\fIgrdfile\fP is used then the grid spacing has
already been initialized; use \fB\-I\fP to override the values.
.UNINDENT
.INDENT 0.0
.TP
\fB\-L\fP\fIlayer\fP
Output only the specified layer (r, g, or b). [Default outputs all 3 layers].
.UNINDENT
.INDENT 0.0
.TP
\fB\-R\fP\fIxmin\fP/\fIxmax\fP/\fIymin\fP/\fIymax\fP[\fB+r\fP][\fB+u\fP\fIunit\fP] (more ...)
Specify the region of interest.  
.UNINDENT
.INDENT 0.0
.TP
\fB\-V\fP[\fIlevel\fP] (more ...)
Select verbosity level [c].  
.UNINDENT
.INDENT 0.0
.TP
\fB\-W\fP\fIwidth\fP/\fIheight\fP[/\fIn_bytes\fP]
Sets the size of the raw raster file. By default an RGB file (which
has 3 bytes/pixel) is assumed. For RGBA files use \fIn_bytes\fP = 4.
Use \fB\-W\fP for guessing the image size of a RGB raw file, and
\fB\-W\fP\fI=/=/4\fP 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.
.UNINDENT
.INDENT 0.0
.TP
\fB\-r\fP (more ...)
Set pixel node registration [gridline].  
.UNINDENT
.INDENT 0.0
.TP
\fB\-^\fP or just \fB\-\fP
Print a short message about the syntax of the command, then exits (NOTE: on Windows just use \fB\-\fP).
.TP
\fB\-+\fP or just \fB+\fP
Print an extensive usage (help) message, including the explanation of
any module\-specific option (but not the GMT common options), then exits.
.TP
\fB\-?\fP or no arguments
Print a complete usage (help) message, including the explanation of all options, then exits.
.UNINDENT
.SH EXAMPLES
.sp
To use the color palette topo.cpt to create r, g, b component grids from
hawaii_grv.nc file, use
.INDENT 0.0
.INDENT 3.5
.INDENT 0.0
.INDENT 3.5
.sp
.nf
.ft C
gmt grd2rgb hawaii_grv.nc \-Ctopo.cpt \-Ghawaii_grv_%c.nc
.ft P
.fi
.UNINDENT
.UNINDENT
.UNINDENT
.UNINDENT
.sp
To output the red component from the Sun raster radiation.ras file, use
.INDENT 0.0
.INDENT 3.5
.INDENT 0.0
.INDENT 3.5
.sp
.nf
.ft C
gmt grd2rgb radiation.ras \-Lr \-Gcomp_%c.nc
.ft P
.fi
.UNINDENT
.UNINDENT
.UNINDENT
.UNINDENT
.SH SEE ALSO
.sp
gmt, gmt.conf,
grdedit, grdimage,
grdmath , grdview
.SH COPYRIGHT
2019, P. Wessel, W. H. F. Smith, R. Scharroo, J. Luis, and F. Wobbe
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