NAME

     grdimage - Create grayshaded or colored  image  from  a  2-D
     netCDF grd file


SYNOPSIS

     grdimage grdfile -Ccptfile -Jparameters  [  -Btickinfo  ]  [
     -Edpi  ] [ -G[f|b]rgb ] [ -Iintensfile] [ -K ] [ -M ] [ -O ]
     [ -P ] [ -Rwest/east/south/north[r] ] [ -Ssearch_radius ]  [
     -T[s]  ] [ -U[/dx/dy/][label] ] [ -V  ] [ -Xx-shift ] [ -Yy-
     shift ] [ -ccopies ]


DESCRIPTION

     grdimage reads a 2-D gridded file and produces a gray-shaded
     (or  colored) map by assigning each contour interval a gray-
     shade (or color).  Optionally, illumination may be added  by
     providing  a  file  with  intensities  in the (-1,+1) range.
     Values outside this range will be clipped.   Such  intensity
     files  can be created from the grdfile using grdgradient and
     modified by grdmath or grdhisteq.   Each  grid-node  in  the
     grdfile  is  represented  as a shaded (or colored) rectangle
     centered on the grid node.  When using map projections,  the
     grid is first resampled on a new rectangular grid  (This can
     be a time-consuming process for large grid  files;  but  see
     -T).   A  24-bit  true color PostScript file is output.  The
     region option can be used to select a map region  larger  or
     smaller than that implied by the extent of the grdfile.

     grdfile
          2-D gridded data set to be imaged

     -C   name of the color palette table

     -J   Selects  the  map  projection.  Scale  is  UNIT/degree,
          1:xxxxx,  or width in UNIT (upper case modifier).  UNIT
          is cm, inch, or m, depending on the  MEASURE_UNIT  set-
          ting in .gmtdefaults, but this can be overridden on the
          command line by  appending  the  c,  i,  or  m  to  the
          scale/width value.

          CYLINDRICAL PROJECTIONS:

          -Jclon0/lat0/scale (Cassini)
          -Jjlon0/scale (Miller)
          -Jmscale (Mercator - Greenwich and Equator as origin)
          -Jmlon0/lat0/scale (Mercator - Give meridian and  stan-
          dard parallel)
          -Joalon0/lat0/azimuth/scale (Oblique Mercator  -  point
          and azimuth)
          -Joblon0/lat0/lon1/lat1/scale (Oblique Mercator  -  two
          points)
          -Joclon0/lat0/lonp/latp/scale (Oblique Mercator - point
          and pole)
          -Jqlon0/scale   (Equidistant   Cylindrical   Projection
          (Plate Carree))
          -Jtlon0/scale (TM - Transverse Mercator,  with  Equator
          as y = 0)
          -Jtlon0/lat0/scale (TM - Transverse Mercator, set  ori-
          gin)
          -Juzone/scale (UTM - Universal Transverse Mercator)
          -Jylon0/lats/scale (Basic Cylindrical Projection)

          AZIMUTHAL PROJECTIONS:

          -Jalon0/lat0/scale (Lambert).
          -Jelon0/lat0/scale (Equidistant).
          -Jflon0/lat0/horizon/scale (Gnomonic).
          -Jglon0/lat0/scale (Orthographic).
          -Jslon0/lat0/scale (General Stereographic)

          CONIC PROJECTIONS:

          -Jblon0/lat0/lat1/lat2/scale (Albers)
          -Jdlon0/lat0/lat1/lat2/scale (Equidistant)
          -Jllon0/lat0/lat1/lat2/scale (Lambert)

          MISCELLANEOUS PROJECTIONS:

          -Jhlon0/scale (Hammer)
          -Jilon0/scale (Sinusoidal)
          -Jk[f|s]lon0/scale (Eckert IV (f) and VI (s))
          -Jnlon0/scale (Robinson)
          -Jrlon0/scale (Winkel Tripel)
          -Jvlon0/scale (Van der Grinten)
          -Jwlon0/scale (Mollweide)

          NON-GEOGRAPHICAL PROJECTIONS:

          -Jpscale[/origin] (polar (theta,r) coordinates, option-
          ally offset theta [0])
          -Jxx-scale[l|ppow][/y-scale[l|ppow]] (Linear, log,  and
          power scaling)
          More details can be found in the psbasemap manpages.


OPTIONS

     No space between the option flag and  the  associated  argu-
     ments.

     -B   Sets map boundary tickmark intervals. See psbasemap for
          details.

     -E   Sets the resolution of the projected grid that will  be
          created if a map projection other than Linear or Merca-
          tor was selected.  By default, the projected grid  will
          be  of  the  same  size (rows and columns) as the input
          file.

     -G   This option only applies when the resulting image  oth-
          erwise  would consist of only two colors: black (0) and
          white (255).  If so, this option will instead  use  the
          image  as a transparent mask and point the mask (or its
          inverse, with -Gb) with the given color combination.

     -I   Gives the name of a grdfile with intensities in the  (-
          1,+1) range. [Default is no illumination].

     -K   More PostScript code will be  appended  later  [Default
          terminates the plot system].

     -M   Force conversion to monochrome image using the (televi-
          sion) YIQ transformation.

     -O   Selects Overlay plot mode [Default  initializes  a  new
          plot system].

     -P   Selects  Portrait  plotting  mode   [GMT   Default   is
          Landscape, see gmtdefaults to change this].

     -R   west, east, south, and  north  specify  the  Region  of
          interest.  To specify boundaries in degrees and minutes
          [and seconds], use the dd:mm[:ss] format.  Append r  if
          lower  left  and  upper right map coordinates are given
          instead of wesn.  You may  ask  for  a  larger  w/e/s/n
          region  to  have  more  room  between the image and the
          axes.  A smaller region than specified in  the  grdfile
          will  result in a subset of the grid [Default is region
          given by the grdfile].

     -S   Set the  search  radius  for  the  averaging  procedure
          [Default avoids aliasing].

     -T   Plot image without any  interpolation.   This  involves
          converting  each node-centered bin into a polygon which
          is then painted separately.  Append  s  to  skip  nodes
          with  z  =  NaN.  This option is useful for categorical
          data where interpolating between values is meaningless.

     -U   Draw Unix System time stamp on plot.  User may  specify
          where the lower left corner of the stamp should fall on
          the  page  relative  to  lower  left  corner  of  plot.
          Optionally,  append  a label, or c (which will plot the
          command string.)

     -V   Selects verbose mode, which will send progress  reports
          to stderr [Default runs "silently"].

     -X -Y
          Shift origin of plot by (x-shift,y-shift).   Prepend  a
          for  absolute  coordinates;  the default (r) will reset
          plot origin.

     -c   Specifies the number of plot copies. [Default is 1]


EXAMPLES

     To gray-shade the file hawaii_grav.grd with shades given  in
     shades.cpt on a Lambert map at 1.5 cm/degree along the stan-
     dard parallels 18 and 24, and using 1 degree tickmarks, try

     grdimage hawaii_grav.grd -Jl18/24/1.5c  -Cshades.cpt  -B1  >
     hawaii_grav_image.ps

     To create an illuminated color PostScript plot of the  grid-
     ded  data  set  image.grd, using the intensities provided by
     the  file  intens.grd,  and  color  levels   in   the   file
     colors.cpt, with linear scaling at 10 inch/x-unit, tickmarks
     every 5 units, try

     grdimage image.grd -Jx10i -Ccolors.cpt  -Iintens.grd  -B5  >
     image.ps


SEE ALSO

     gmt(l),    grdcontour(l),    grdview(l),     grdgradient(l),
     grdhisteq(l)