NAME
grdimage - Create grayshaded or colored image from a 2-D
netCDF grd file
SYNOPSIS
grdimage grdfile -Ccptfile -Jparameters [ -Btickinfo ] [ -
Edpi ] [ -Fred/green/blue ] [ -Iintensfile] [ -K ] [ -M ] [
- O ] [ - P ] [ - Rwest/east/south/north[r] ] [ -
U[/dx/dy/][label] ] [ -V ] [ -Xx-shift ] [ -Yy-shift ] [ -
ccopies ] [ -0 || -1 || -2 ]
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 using one of three
methods. 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)
-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)
-Juzone/scale (UTM - Universal Transverse Mercator)
-Jylon0/lats/scale (Basic Cylindrical Projection)
AZIMUTHAL PROJECTIONS:
-Jalon0/lat0/scale (Lambert).
-Jelon0/lat0/scale (Equidistant).
-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) coordi-
nates)
-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.
-F Sets the color used for Frame and annotation. [Default
is black]
-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 (telev-
ision) 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 (-0.75,-0.75)]. 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 (1,1) for new plots, (0,0) for overlays].
-c Specifies the number of plot copies. [Default is 1]
-0 Create the image using the Adobe PostScript colorimage
operator. This is the GMT default (which can be modi-
fied in the .gmtdefaults file).
-1 Create the image by plotting individually colored
tiles.
-2 Create the image by color separation using three calls
to image for later processing by psto24.
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 -Jl18/24/0.5 - 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, and using color separations for use with
psto24, try
grdimage image.grd -Jx10 -Ccolors.cpt -Iintens.grd -B5 -2 >
image.ps
BUGS
Having three separate ways of creating the colorimage comes
from the fact that many different implementations of the
colorimage PostScript operator exists for a wide variety of
hardcopy devices. The three options allow you to create the
type of output required by your RIP.
SEE ALSO
gmt, grdcontour, grdview, grdgradient, grdhisteq, ps2ras,
psto24
REFERENCES
Wessel, P., and W. H. F. Smith, 1995, The Generic Mapping
Tools (GMT) version 3.0 Technical Reference & Cookbook,
SOEST/NOAA.
Wessel, P., and W. H. F. Smith, 1995, New Version of the
Generic Mapping Tools Released, EOS Trans. AGU, 76, p. 329.
Wessel, P., and W. H. F. Smith, 1995, New Version of the
Generic Mapping Tools Released,
http://www.agu.org/eos_elec/95154e.html, Copyright 1995 by
the American Geophysical Union.
Wessel, P., and W. H. F. Smith, 1991, Free Software Helps
Map and Display Data, EOS Trans. AGU, 72, p. 441.