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<title>GRDIMAGE</title>
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<h1 align=center>GRDIMAGE</h1>
<a href="#NAME">NAME</a><br>
<a href="#SYNOPSIS">SYNOPSIS</a><br>
<a href="#DESCRIPTION">DESCRIPTION</a><br>
<a href="#OPTIONS">OPTIONS</a><br>
<a href="#GRID FILE FORMATS">GRID FILE FORMATS</a><br>
<a href="#IMAGING GRIDS WITH NANS">IMAGING GRIDS WITH NANS</a><br>
<a href="#EXAMPLES">EXAMPLES</a><br>
<a href="#SEE ALSO">SEE ALSO</a><br>
<hr>
<a name="NAME"></a>
<h2>NAME</h2>
<p style="margin-left:11%; margin-top: 1em">grdimage
− Create grayshaded or colored image from a 2-D netCDF
grid file</p>
<a name="SYNOPSIS"></a>
<h2>SYNOPSIS</h2>
<p style="margin-left:11%; margin-top: 1em"><b>grdimage</b>
<i>grd_z</i> | <i>grd_r grd_g grd_b</i>
<b>−C</b><i>cptfile</i> [ <b>−D</b>[<b>r</b>] ]
<b>−J</b><i>parameters</i> [
<b>−B</b>[<b>p</b>|<b>s</b>]<i>parameters</i> ] [
<b>−Ei</b>|<i>dpi</i> ] [
<b>−G</b>[<b>f</b>|<b>b</b>]<i>color</i> ] [
<b>−I</b><i>intensfile</i> ] [ <b>−K</b> ] [
<b>−M</b> ] [ <b>−N</b> ] [ <b>−O</b> ] [
<b>−P</b> ] [ <b>−Q</b> ] [
<b>−R</b><i>west</i>/<i>east</i>/<i>south</i>/<i>north</i>[<b>r</b>]
] [
<b>−S</b>[<b>-</b>]<b>b</b>|<b>c</b>|<b>l</b>|<b>n</b>[<b>/</b><i>threshold</i>]
] [ <b>−T</b> ] [
<b>−U</b>[<i>just</i>/<i>dx</i>/<i>dy</i>/][<b>c</b>|<i>label</i>]
] [ <b>−V</b> ] [
<b>−X</b>[<b>a</b>|<b>c</b>|<b>r</b>][<i>x-shift</i>[<b>u</b>]]
] [
<b>−Y</b>[<b>a</b>|<b>c</b>|<b>r</b>][<i>y-shift</i>[<b>u</b>]]
] [ <b>−c</b><i>copies</i> ] [
<b>−f</b>[<b>i</b>|<b>o</b>]<i>colinfo</i> ] [
<b>−r</b> ]</p>
<a name="DESCRIPTION"></a>
<h2>DESCRIPTION</h2>
<p style="margin-left:11%; margin-top: 1em"><b>grdimage</b>
reads one 2-D grid file and produces a gray-shaded (or
colored) map by plotting rectangles centered on each grid
node and assigning them a gray-shade (or color) based on the
z-value. Alternatively, <b>grdimage</b> reads three 2-D grid
files with the red, green, and blue components directly (all
must be in the 0-255 range). 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 grid using
<b><A HREF="grdgradient.html">grdgradient</A></b> and, optionally, modified by
<b><A HREF="grdmath.html">grdmath</A></b> or <b><A HREF="grdhisteq.html">grdhisteq</A></b>. <br>
When using map projections, the grid is first resampled on a
new rectangular grid with the same dimensions. Higher
resolution images can be obtained by using the
<b>−E</b> option. To obtain the resampled value (and
hence shade or color) of each map pixel, its location is
inversely projected back onto the input grid after which a
value is interpolated between the surrounding input grid
values. By default bi-cubic interpolation is used. Aliasing
is avoided by also forward projecting the input grid nodes.
If two or more nodes are projected onto the same pixel,
their average will dominate in the calculation of the pixel
value. Interpolation and aliasing is controlled with the
<b>−S</b> option. <br>
The <b>−R</b> option can be used to select a map
region larger or smaller than that implied by the extent of
the grid. <br>
A (color) <i>PostScript</i> file is output. <i><br>
grd_z</i> | <i>grd_r grd_g grd_b</i></p>
<p style="margin-left:22%;">2-D gridded data set (or red,
green, blue grids) to be imaged (See GRID FILE FORMATS
below.)</p>
<table width="100%" border=0 rules="none" frame="void"
cellspacing="0" cellpadding="0">
<tr valign="top" align="left">
<td width="11%"></td>
<td width="3%">
<p style="margin-top: 1em" valign="top"><b>−C</b></p> </td>
<td width="8%"></td>
<td width="78%">
<p style="margin-top: 1em" valign="top">name of the color
palette table (for <i>grd_z</i> only).</p></td>
<tr valign="top" align="left">
<td width="11%"></td>
<td width="3%">
<p style="margin-top: 1em" valign="top"><b>−J</b></p> </td>
<td width="8%"></td>
<td width="78%">
<p style="margin-top: 1em" valign="top">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 <b><A HREF="gmtdefaults.html#MEASURE_UNIT">MEASURE_UNIT</A></b> setting in .gmtdefaults4, but this
can be overridden on the command line by appending <b>c</b>,
<b>i</b>, or <b>m</b> to the scale/width value. When central
meridian is optional, default is center of longitude range
on <b>−R</b> option. Default standard parallel is the
equator. For map height, max dimension, or min dimension,
append <b>h</b>, <b>+</b>, or <b>-</b> to the width,
respectively.</p> </td>
</table>
<p style="margin-left:22%;">More details can be found in
the <b><A HREF="psbasemap.html">psbasemap</A></b> man pages.</p>
<p style="margin-left:22%; margin-top: 1em"><b>CYLINDRICAL
PROJECTIONS:</b></p>
<p style="margin-left:22%; margin-top: 1em"><b>−Jc</b><i>lon0/lat0/scale</i>
(Cassini) <b><br>
−Jcyl_stere</b>/[<i>lon0/</i>[<i>lat0/</i>]]<i>scale</i>
(Cylindrical Stereographic) <b><br>
−Jj</b>[<i>lon0/</i>]<i>scale</i> (Miller) <b><br>
−Jm</b>[<i>lon0</i>/[<i>lat0/</i>]]<i>scale</i>
(Mercator) <b><br>
−Jm</b><i>lon0/lat0/scale</i> (Mercator - Give
meridian and standard parallel) <b><br>
−Jo</b>[<b>a</b>]<i>lon0/lat0/azimuth/scale</i>
(Oblique Mercator - point and azimuth) <b><br>
−Jo</b>[<b>b</b>]<i>lon0/lat0/lon1/lat1/scale</i>
(Oblique Mercator - two points) <b><br>
−Joc</b><i>lon0/lat0/lonp/latp/scale</i> (Oblique
Mercator - point and pole) <b><br>
−Jq</b>[<i>lon0/</i>[<i>lat0/</i>]]<i>scale</i>
(Cylindrical Equidistant) <b><br>
−Jt</b><i>lon0/</i>[<i>lat0/</i>]<i>scale</i> (TM -
Transverse Mercator) <b><br>
−Ju</b><i>zone/scale</i> (UTM - Universal Transverse
Mercator) <b><br>
−Jy</b>[<i>lon0/</i>[<i>lat0/</i>]]<i>scale</i>
(Cylindrical Equal-Area)</p>
<p style="margin-left:22%; margin-top: 1em"><b>CONIC
PROJECTIONS:</b></p>
<p style="margin-left:22%; margin-top: 1em"><b>−Jb</b><i>lon0/lat0/lat1/lat2/scale</i>
(Albers) <b><br>
−Jd</b><i>lon0/lat0/lat1/lat2/scale</i> (Conic
Equidistant) <b><br>
−Jl</b><i>lon0/lat0/lat1/lat2/scale</i> (Lambert Conic
Conformal) <b><br>
−Jpoly</b>/[<i>lon0/</i>[<i>lat0/</i>]]<i>scale</i>
((American) Polyconic)</p>
<p style="margin-left:22%; margin-top: 1em"><b>AZIMUTHAL
PROJECTIONS:</b></p>
<p style="margin-left:22%; margin-top: 1em"><b>−Ja</b><i>lon0/lat0</i>[<i>/horizon</i>]<i>/scale</i>
(Lambert Azimuthal Equal-Area) <b><br>
−Je</b><i>lon0/lat0</i>[<i>/horizon</i>]<i>/scale</i>
(Azimuthal Equidistant) <b><br>
−Jf</b><i>lon0/lat0</i>[<i>/horizon</i>]<i>/scale</i>
(Gnomonic) <b><br>
−Jg</b><i>lon0/lat0</i>[<i>/horizon</i>]<i>/scale</i>
(Orthographic) <b><br>
−Jg</b><i>lon0/lat0/altitude/azimuth/tilt/twist/Width/Height/scale</i>
(General Perspective). <b><br>
−Js</b><i>lon0/lat0</i>[<i>/horizon</i>]<i>/scale</i>
(General Stereographic)</p>
<p style="margin-left:22%; margin-top: 1em"><b>MISCELLANEOUS
PROJECTIONS:</b></p>
<p style="margin-left:22%; margin-top: 1em"><b>−Jh</b>[<i>lon0/</i>]<i>scale</i>
(Hammer) <b><br>
−Ji</b>[<i>lon0/</i>]<i>scale</i> (Sinusoidal) <b><br>
−Jkf</b>[<i>lon0/</i>]<i>scale</i> (Eckert IV) <b><br>
−Jk</b>[<b>s</b>][<i>lon0/</i>]<i>scale</i> (Eckert
VI) <b><br>
−Jn</b>[<i>lon0/</i>]<i>scale</i> (Robinson) <b><br>
−Jr</b>[<i>lon0/</i>]<i>scale</i> (Winkel Tripel)
<b><br>
−Jv</b>[<i>lon0/</i>]<i>scale</i> (Van der Grinten)
<b><br>
−Jw</b>[<i>lon0/</i>]<i>scale</i> (Mollweide)</p>
<p style="margin-left:22%; margin-top: 1em"><b>NON-GEOGRAPHICAL
PROJECTIONS:</b></p>
<p style="margin-left:22%; margin-top: 1em"><b>−Jp</b>[<b>a</b>]<i>scale</i>[<i>/origin</i>][<b>r</b>|<b>z</b>]
(Polar coordinates (theta,r)) <b><br>
−Jx</b><i>x-scale</i>[<b>d</b>|<b>l</b>|<b>p</b><i>pow</i>|<b>t</b>|<b>T</b>][<i>/y-scale</i>[<b>d</b>|<b>l</b>|<b>p</b><i>pow</i>|<b>t</b>|<b>T</b>]]
(Linear, log, and power scaling)</p>
<a name="OPTIONS"></a>
<h2>OPTIONS</h2>
<p style="margin-left:11%; margin-top: 1em">No space
between the option flag and the associated arguments.</p>
<table width="100%" border=0 rules="none" frame="void"
cellspacing="0" cellpadding="0">
<tr valign="top" align="left">
<td width="11%"></td>
<td width="7%">
<p style="margin-top: 1em" valign="top"><b>−B</b></p> </td>
<td width="4%"></td>
<td width="78%">
<p style="margin-top: 1em" valign="top">Sets map boundary
annotation and tickmark intervals; see the <b><A HREF="psbasemap.html">psbasemap</A></b>
man page for all the details.</p></td>
<tr valign="top" align="left">
<td width="11%"></td>
<td width="7%">
<p style="margin-top: 1em" valign="top"><b>−D</b></p> </td>
<td width="4%"></td>
<td width="78%">
<p style="margin-top: 1em" valign="top">Specifies that the
grid supplied is an image file to be read via GDAL.
Obviously this option will work only with <b><A HREF="GMT.html">GMT</A></b>
versions built with GDAL support. The image can be indexed
or true color (RGB) and can be an URL of a remotely located
file. That is <b>−D</b>
http://www.somewhere.com/image.jpg is a valid file syntax.
Note, however, that to use it this way you must not be
blocked by a proxy. If you are, chances are good that it can
work by setting the environmental variable http_proxy with
the value ’your_proxy:port’ Append <b>r</b> to
use the region specified by <b>−R</b> to apply to the
image. For example, if you have used <b>−Rd</b> then
the image will be assigned the limits of a global domain.
The interest of this mode is that you can project a raw
image (an image without referencing coordinates).</p></td>
<tr valign="top" align="left">
<td width="11%"></td>
<td width="7%">
<p style="margin-top: 1em" valign="top"><b>−E</b></p> </td>
<td width="4%"></td>
<td width="78%">
<p style="margin-top: 1em" valign="top">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. Specify <b>i</b> to use the
<i>PostScript</i> image operator to interpolate the image at
the device resolution.</p></td>
<tr valign="top" align="left">
<td width="11%"></td>
<td width="7%">
<p style="margin-top: 1em" valign="top"><b>−G</b></p> </td>
<td width="4%"></td>
<td width="78%">
<p style="margin-top: 1em" valign="top">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
paint the mask (or its inverse, with <b>−Gb</b>) with
the given color combination. (See SPECIFYING COLOR
below).</p> </td>
<tr valign="top" align="left">
<td width="11%"></td>
<td width="7%">
<p style="margin-top: 1em" valign="top"><b>−I</b></p> </td>
<td width="4%"></td>
<td width="78%">
<p style="margin-top: 1em" valign="top">Gives the name of a
grid file with intensities in the (-1,+1) range. [Default is
no illumination].</p></td>
<tr valign="top" align="left">
<td width="11%"></td>
<td width="7%">
<p style="margin-top: 1em" valign="top"><b>−K</b></p> </td>
<td width="4%"></td>
<td width="78%">
<p style="margin-top: 1em" valign="top">More
<i>PostScript</i> code will be appended later [Default
terminates the plot system].</p></td>
<tr valign="top" align="left">
<td width="11%"></td>
<td width="7%">
<p style="margin-top: 1em" valign="top"><b>−M</b></p> </td>
<td width="4%"></td>
<td width="78%">
<p style="margin-top: 1em" valign="top">Force conversion to
monochrome image using the (television) YIQ transformation.
Cannot be used with <b>−Q</b>.</p></td>
<tr valign="top" align="left">
<td width="11%"></td>
<td width="7%">
<p style="margin-top: 1em" valign="top"><b>−N</b></p> </td>
<td width="4%"></td>
<td width="78%">
<p style="margin-top: 1em" valign="top">Do not clip the
image at the map boundary (only relevant for non-rectangular
maps).</p> </td>
<tr valign="top" align="left">
<td width="11%"></td>
<td width="7%">
<p style="margin-top: 1em" valign="top"><b>−O</b></p> </td>
<td width="4%"></td>
<td width="78%">
<p style="margin-top: 1em" valign="top">Selects Overlay
plot mode [Default initializes a new plot system].</p></td>
<tr valign="top" align="left">
<td width="11%"></td>
<td width="7%">
<p style="margin-top: 1em" valign="top"><b>−P</b></p> </td>
<td width="4%"></td>
<td width="78%">
<p style="margin-top: 1em" valign="top">Selects Portrait
plotting mode [Default is Landscape, see <b><A HREF="gmtdefaults.html">gmtdefaults</A></b>
to change this].</p></td>
<tr valign="top" align="left">
<td width="11%"></td>
<td width="7%">
<p style="margin-top: 1em" valign="top"><b>−Q</b></p> </td>
<td width="4%"></td>
<td width="78%">
<p style="margin-top: 1em" valign="top">Make grid nodes
with z = NaN transparent, using the colormasking feature in
<i>PostScript</i> Level 3 (the PS device must support PS
Level 3).</p></td>
<tr valign="top" align="left">
<td width="11%"></td>
<td width="7%">
<p style="margin-top: 1em" valign="top"><b>−R</b></p> </td>
<td width="4%"></td>
<td width="78%">
<p style="margin-top: 1em" valign="top"><i>xmin</i>,
<i>xmax</i>, <i>ymin</i>, and <i>ymax</i> specify the Region
of interest. For geographic regions, these limits correspond
to <i>west, east, south,</i> and <i>north</i> and you may
specify them in decimal degrees or in
[+-]dd:mm[:ss.xxx][W|E|S|N] format. Append <b>r</b> if lower
left and upper right map coordinates are given instead of
w/e/s/n. The two shorthands <b>−Rg</b> and
<b>−Rd</b> stand for global domain (0/360 and
-180/+180 in longitude respectively, with -90/+90 in
latitude). Alternatively, specify the name of an existing
grid file and the <b>−R</b> settings (and grid
spacing, if applicable) are copied from the grid. For
calendar time coordinates you may either give (a) relative
time (relative to the selected <b><A HREF="gmtdefaults.html#TIME_EPOCH">TIME_EPOCH</A></b> and in the
selected <b><A HREF="gmtdefaults.html#TIME_UNIT">TIME_UNIT</A></b>; append <b>t</b> to
<b>−JX</b>|<b>x</b>), or (b) absolute time of the form
[<i>date</i>]<b>T</b>[<i>clock</i>] (append <b>T</b> to
<b>−JX</b>|<b>x</b>). At least one of <i>date</i> and
<i>clock</i> must be present; the <b>T</b> is always
required. The <i>date</i> string must be of the form
[-]yyyy[-mm[-dd]] (Gregorian calendar) or yyyy[-Www[-d]]
(ISO week calendar), while the <i>clock</i> string must be
of the form hh:mm:ss[.xxx]. The use of delimiters and their
type and positions must be exactly as indicated (however,
input, output and plot formats are customizable; see
<b><A HREF="gmtdefaults.html">gmtdefaults</A></b>). You may ask for a larger <i>w/e/s/n</i>
region to have more room between the image and the axes. A
smaller region than specified in the grid file will result
in a subset of the grid [Default is the region given by the
grid file].</p></td>
<tr valign="top" align="left">
<td width="11%"></td>
<td width="7%">
<p style="margin-top: 1em" valign="top"><b>−S</b></p> </td>
<td width="4%"></td>
<td width="78%">
<p style="margin-top: 1em" valign="top">Select the
interpolation mode by adding <b>b</b> for B-spline
smoothing, <b>c</b> for bicubic interpolation, <b>l</b> for
bilinear interpolation, or <b>n</b> for nearest-neighbor
value (for example to plot categorical data). Optionally,
prepend <b>-</b> to switch off antialiasing. Add
<b>/</b><i>threshold</i> to control how close to nodes with
NaNs the interpolation will go. A <i>threshold</i> of 1.0
requires all (4 or 16) nodes involved in interpolation to be
non-NaN. 0.5 will interpolate about half way from a non-NaN
value; 0.1 will go about 90% of the way, etc. [Default is
bicubic interpolation with antialiasing and a threshold of
0.5].</p> </td>
<tr valign="top" align="left">
<td width="11%"></td>
<td width="7%">
<p style="margin-top: 1em" valign="top"><b>−T</b></p> </td>
<td width="4%"></td>
<td width="78%">
<p style="margin-top: 1em" valign="top">This option has
become OBSOLETE. Use <b>grdview −T</b> instead. Use
<b>−Sn</b> to plot near-neighbor values only (use
<b>−E</b> to increase the resolution). Use
<b>−Sn −Q</b> to obtain something similar to the
old option <b>−Ts</b>. The option <b>−To</b> is
no longer supported.</p></td>
<tr valign="top" align="left">
<td width="11%"></td>
<td width="7%">
<p style="margin-top: 1em" valign="top"><b>−U</b></p> </td>
<td width="4%"></td>
<td width="78%">
<p style="margin-top: 1em" valign="top">Draw Unix System
time stamp on plot. By adding <i>just/dx/dy/</i>, the user
may specify the justification of the stamp and where the
stamp should fall on the page relative to lower left corner
of the plot. For example, BL/0/0 will align the lower left
corner of the time stamp with the lower left corner of the
plot. Optionally, append a <i>label</i>, or <b>c</b> (which
will plot the command string.). The <b><A HREF="GMT.html">GMT</A></b> parameters
<b><A HREF="gmtdefaults.html#UNIX_TIME">UNIX_TIME</A></b>, <b><A HREF="gmtdefaults.html#UNIX_TIME_POS">UNIX_TIME_POS</A></b>, and
<b><A HREF="gmtdefaults.html#UNIX_TIME_FORMAT">UNIX_TIME_FORMAT</A></b> can affect the appearance; see the
<b><A HREF="gmtdefaults.html">gmtdefaults</A></b> man page for details. The time string
will be in the locale set by the environment variable
<b>TZ</b> (generally local time).</p></td>
<tr valign="top" align="left">
<td width="11%"></td>
<td width="7%">
<p style="margin-top: 1em" valign="top"><b>−V</b></p> </td>
<td width="4%"></td>
<td width="78%">
<p style="margin-top: 1em" valign="top">Selects verbose
mode, which will send progress reports to stderr [Default
runs "silently"].</p></td>
<tr valign="top" align="left">
<td width="11%"></td>
<td width="7%">
<p style="margin-top: 1em" valign="top"><b>−X
−Y</b></p> </td>
<td width="4%"></td>
<td width="78%">
<p style="margin-top: 1em" valign="top">Shift plot origin
relative to the current origin by (<i>x-shift,y-shift</i>)
and optionally append the length unit (<b>c</b>, <b>i</b>,
<b>m</b>, <b>p</b>). You can prepend <b>a</b> to shift the
origin back to the original position after plotting, or
prepend <b>r</b> [Default] to reset the current origin to
the new location. If <b>−O</b> is used then the
default (<i>x-shift,y-shift</i>) is (0,0), otherwise it is
(r1i, r1i) or (r2.5c, r2.5c). Alternatively, give <b>c</b>
to align the center coordinate (x or y) of the plot with the
center of the page based on current page size.</p></td>
<tr valign="top" align="left">
<td width="11%"></td>
<td width="7%">
<p style="margin-top: 1em" valign="top"><b>−c</b></p> </td>
<td width="4%"></td>
<td width="78%">
<p style="margin-top: 1em" valign="top">Specifies the
number of plot copies. [Default is 1].</p></td>
<tr valign="top" align="left">
<td width="11%"></td>
<td width="7%">
<p style="margin-top: 1em" valign="top"><b>−f</b></p> </td>
<td width="4%"></td>
<td width="78%">
<p style="margin-top: 1em" valign="top">Special formatting
of input and/or output columns (time or geographical data).
Specify <b>i</b> or <b>o</b> to make this apply only to
input or output [Default applies to both]. Give one or more
columns (or column ranges) separated by commas. Append
<b>T</b> (absolute calendar time), <b>t</b> (relative time
in chosen <b><A HREF="gmtdefaults.html#TIME_UNIT">TIME_UNIT</A></b> since <b><A HREF="gmtdefaults.html#TIME_EPOCH">TIME_EPOCH</A></b>),
<b>x</b> (longitude), <b>y</b> (latitude), or <b>f</b>
(floating point) to each column or column range item.
Shorthand <b>−f</b>[<b>i</b>|<b>o</b>]<b>g</b> means
<b>−f</b>[<b>i</b>|<b>o</b>]0<b>x</b>,1<b>y</b>
(geographic coordinates).</p></td>
</table>
<a name="GRID FILE FORMATS"></a>
<h2>GRID FILE FORMATS</h2>
<p style="margin-left:11%; margin-top: 1em"><b><A HREF="GMT.html">GMT</A></b> is
able to recognize many of the commonly used grid file
formats, as well as the precision, scale and offset of the
values contained in the grid file. When <b><A HREF="GMT.html">GMT</A></b> needs a
little help with that, you can add the suffix
<b>=</b><i>id</i>[<b>/</b><i>scale</i><b>/</b><i>offset</i>[<b>/</b><i>nan</i>]],
where <i>id</i> is a two-letter identifier of the grid type
and precision, and <i>scale</i> and <i>offset</i> are
optional scale factor and offset to be applied to all grid
values, and <i>nan</i> is the value used to indicate missing
data. See <b><A HREF="grdreformat.html">grdreformat</A></b>(1) and Section 4.17 of the GMT
Technical Reference and Cookbook for more information.</p>
<p style="margin-left:11%; margin-top: 1em">When reading a
netCDF file that contains multiple grids, <b><A HREF="GMT.html">GMT</A></b> will
read, by default, the first 2-dimensional grid that can find
in that file. To coax <b><A HREF="GMT.html">GMT</A></b> into reading another
multi-dimensional variable in the grid file, append
<b>?</b><i>varname</i> to the file name, where
<i>varname</i> is the name of the variable. Note that you
may need to escape the special meaning of <b>?</b> in your
shell program by putting a backslash in front of it, or by
placing the filename and suffix between quotes or double
quotes. See <b><A HREF="grdreformat.html">grdreformat</A></b>(1) and Section 4.18 of the
GMT Technical Reference and Cookbook for more information,
particularly on how to read splices of 3-, 4-, or
5-dimensional grids.</p>
<a name="IMAGING GRIDS WITH NANS"></a>
<h2>IMAGING GRIDS WITH NANS</h2>
<p style="margin-left:11%; margin-top: 1em">Be aware that
if your input grid contains patches of NaNs, these patches
can become larger as a consequence of the resampling that
must take place with most map projections. Because
<b>grdimage</b> uses the <i>PostScript</i> colorimage
operator, for most non-linear projections we must resample
your grid onto an equidistant rectangular lattice. If you
find that the NaN areas are not treated adequately, consider
(a) use a linear projection, or (b) use <b>grdview
−Ts</b> instead.</p>
<a name="EXAMPLES"></a>
<h2>EXAMPLES</h2>
<p style="margin-left:11%; margin-top: 1em">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:</p>
<p style="margin-left:11%; margin-top: 1em"><b>grdimage</b>
hawaii_grav.grd <b>−Jl</b> 18/24/1.5<b>c −C</b>
shades.cpt <b>−B</b> 1 > hawaii_grav_image.ps</p>
<p style="margin-left:11%; margin-top: 1em">To create an
illuminated color <i>PostScript</i> 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:</p>
<p style="margin-left:11%; margin-top: 1em"><b>grdimage</b>
image.grd <b>−Jx</b> 10<b>i −C</b> colors.cpt
<b>−I</b> intens.grd <b>−B</b> 5 >
image.ps</p>
<p style="margin-left:11%; margin-top: 1em">To create an
false color <i>PostScript</i> plot from the three grid files
red.grd, green.grd, and blue.grd, with linear scaling at 10
inch/x-unit, tickmarks every 5 units:</p>
<p style="margin-left:11%; margin-top: 1em"><b>grdimage</b>
red.grd green.grd blue.grd <b>−Jx</b> 10<b>i
−B</b> 5 > rgbimage.ps</p>
<p style="margin-left:11%; margin-top: 1em">When GDAL
support is built in: To create a sinusoidal projection of a
remotely located Jessica Rabbit</p>
<p style="margin-left:11%; margin-top: 1em"><b>grdimage</b>
-JI15c -Rd -Dr
http://larryfire.files.wordpress.com/2009/07/untooned_jessicarabbit.jpg
-P > jess.ps</p>
<a name="SEE ALSO"></a>
<h2>SEE ALSO</h2>
<p style="margin-left:11%; margin-top: 1em"><i><A HREF="GMT.html">GMT</A></i>(1),
<i><A HREF="gmt2rgb.html">gmt2rgb</A></i>(1), <i><A HREF="grdcontour.html">grdcontour</A></i>(1), <i><A HREF="grdview.html">grdview</A></i>(1),
<i><A HREF="grdgradient.html">grdgradient</A></i>(1), <i><A HREF="grdhisteq.html">grdhisteq</A></i>(1)</p>
<hr>
</body>
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