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grdimage - Create grayshaded or colored image from a 2-D netCDF grd file
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 ]
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.
No space between the option flag and the associated arguments.
- 2-D gridded data set to be imaged
- name of the color palette table
- 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.
-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)
-Jslon0/lat0/[slat/]scale (General Stereographic)
-Jk[f|s]lon0/scale (Eckert IV (f) and VI (s))
-Jrlon0/scale (Winkel Tripel)
-Jvlon0/scale (Van der Grinten)
-Jp[a]scale[/origin] (polar (theta,r) coordinates, optional a for azimuths
and offset theta )
-Jxx-scale[l|ppow][/y-scale[l|ppow]] (Linear, log, and power scaling)
More details can be found in the psbasemap manpages.
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
- Sets map boundary tickmark intervals. See psbasemap for details.
- 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.
- 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.
- Gives the name of a grdfile with
intensities in the (-1,+1) range. [Default is no illumination].
- More PostScript
code will be appended later [Default terminates the plot system].
conversion to monochrome image using the (television) YIQ transformation.
- Selects Overlay plot mode [Default initializes a new plot system].
Portrait plotting mode [GMT Default is Landscape, see gmtdefaults to change
- 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].
- Set the search radius for the averaging procedure [Default avoids aliasing].
- 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.
- 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.)
- Selects verbose mode, which
will send progress reports to stderr [Default runs "silently"].
- -X -Y
origin of plot by (x-shift,y-shift). Prepend a for absolute coordinates; the
default (r) will reset plot origin.
- Specifies the number of plot copies.
[Default is 1]
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
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