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<TITLE>grd2cpt</TITLE>
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<H1>grd2cpt</H1>
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<PRE>
<!-- Manpage converted by man2html 3.0.1 -->
grd2cpt - Read a grdfile and make a color palette file
</PRE>
<H2>SYNOPSIS</H2><PRE>
<B>grd2cpt</B> <I>grdfile</I> [ <B>-C</B><I>cptmaster</I> ] [ <B>-I</B> ] [ <B>-L</B><I>min</I>
<I>limit/maxlimit</I> ] [ <B>-S</B><I>zstart/zstop/zinc</I> ] [ <B>-V</B> ] [ <B>-Z</B> ]
</PRE>
<H2>DESCRIPTION</H2><PRE>
<B>grd2cpt</B> reads a grdfile and writes a color palette (cpt)
file to standard output. The cpt file is based on an
existing master cptfile of your choice, and the mapping
from data value to colors is through the data's cumulative
distribution function (CDF), so that the colors are' his
togram equalized. Thus if the resulting cpt file is used
with the grdfile and grdimage with a linear projection,
the colors will be uniformly distributed in area on the
plot. Let z be the data values in the grdfile. Define
CDF(Z) = (# of z < Z) / (# of z in grdfile). (NaNs are
ignored). These z-values are then normalized to the mas
ter cptfile and colors are sampled at the desired inter
vals.
<I>grdfile</I>
The 2-D binary grdfile used to derive the color
palette table.
</PRE>
<H2>OPTIONS</H2><PRE>
<B>-C</B> Selects the master color table to use in the inter
polation. Choose among the built-in tables (type
<B>grd2cpt</B> to see the list) or give the name of an
existing cptfile [Default gives a rainbow cpt
file].
<B>-I</B> Reverses the sense of color progression in the mas
ter cptfile.
<B>-L</B> Limit range of cptfile to <I>minlimit/maxlimit</I>, and
don't count data' outside range when estimating
CDF(Z). [Default uses min and max of data.]
<B>-S</B> Set steps in cpt file. Calculate entries in cptfile
from <I>zstart</I> to <I>zstop</I> in steps of (<I>zinc</I>). [Default
chooses arbitrary values by a crazy scheme.] .TP <B>-V</B>
Verbose operation. This will write CDF(Z) estimates
to stderr. [Default is silent.]
</PRE>
<H2>EXAMPLES</H2><PRE>
Sometimes you don't want to make a cpt file (yet) but
would find it helpful' to know that 90% of your data lie
between z1 and z2, something you cannot learn from
<B><A HREF="grdinfo.html">grdinfo</A></B>. So you can do this to see some points on the
CDF(Z) curve (use <B>-V</B> option to see more):
20, and ignore data below zero in computing CDF(Z), and
use the built-in master cptfile relief, try
grd2cpt mydata.grd <B>-C</B><I>relief</I> <B>-L</B>0/10000 <B>-S</B>0/200/20 >
mydata.cpt
</PRE>
<H2>SEE ALSO</H2><PRE>
<I><A HREF="gmtdefaults.html">gmtdefaults</A></I>(l), <I>gmt</I>(l), <I><A HREF="grdhisteq.html">grdhisteq</A></I>(l), <I><A HREF="grdinfo.html">grdinfo</A></I>(l),
<I><A HREF="makecpt.html">makecpt</A></I>(l)
</PRE>
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