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)