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 setting 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 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, with Equator as y = 0)
              -Jtlon0/lat0/scale (TM - Transverse Mercator, set origin)
              -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/[slat/]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:

              -Jp[a]scale[/origin]  (polar  (theta,r)  coordinates,  optional  a for azimuths and
              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 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.

       -G     This option only applies when the resulting image otherwise 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 (television) YIQ transformation.

       -bo    Selects binary output. Append s for single precision [Default is double].

       -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.). The GMT
              parameters  UNIX_TIME  and  UNIX_TIME_POS  can  affect  the  appearance;  see   the
              gmtdefaults man page for details.

       -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 standard 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 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(1gmt), grdcontour(1gmt), grdview(1gmt), grdgradient(1gmt), grdhisteq(1gmt)

                                            1 Jan 2004                                GRDIMAGE(l)