NAME

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

SYNOPSIS

      grdimage grdfile -Ccptfile -Jparameters [ -Btickinfo ] [ -Edpi ] [
      -Iintensfile] [ -K ] [ -M ] [ -O ] [ -P ] [ -Rwest/east/south/north[r]
      ] [ -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).  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 inch/degree, 1:xxxxx, or
           width in inch (upper case modifier).

           CYLINDRICAL PROJECTIONS:

           -Jclon0/lat0/scale (Cassini)
           -Jjlon0/scale (Miller)
           -Jmscale (Mercator - Greenwich and Equator as origin)
           -Jmlon0/lat0/scale (Mercator - Give meridian and standard
           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)
           -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)
           -Jllon0/lat0/lat1/lat2/scale (Lambert)

           MISCELLANEOUS PROJECTIONS:

           -Jhlon0/scale (Hammer)
           -Jilon0/scale (Sinusoidal)
           -Jklon0/scale (Eckert VI)
           -Jnlon0/scale (Robinson)
           -Jrlon0/scale (Winkel Tripel)
           -Jwlon0/scale (Mollweide)

           NON-GEOGRAPHICAL PROJECTIONS:

           -Jpscale (Linear projection for polar (theta,r) coordinates)
           -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 arguments.

      -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 Mercator was selected.  By
           default, the projected grid will be of the same size (rows and
           columns) as the input file.

      -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 (television) 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].

      -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 in inch [Default is (-0.75i/-
           0.75i)].  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) inch  [Default is
           (a1i,a1i) for new plots, (0,0) for overlays].  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 0.5 inch/degree along the standard parallels 18
      and 24, and using 1 degree tickmarks, try

      grdimage hawaii_grav.grd -Jl18/24/0.5i -Cshades.cpt -B1 >
      hawaii_grav_image.ps

      To create an illuminated color PostScript plot of the gridded 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, grdcontour, grdview, grdgradient, grdhisteq