(19) Color patterns on maps

GMT 3.1 introduced color patterns and this examples give a few cases of how to use this new feature. We make a phony poster that advertises an international conference on GMT in Honolulu. We use grdmath, makecpt, and grdimage to draw pleasing color backgrounds on maps, and overlay pscoast clip paths to have the patterns change at the coastlines. The middle panel demonstrates a simple pscoast call where the built-in pattern # 86 is drawn at 100 dpi but with the black and white pixels replaced with color combinations. At the same time the ocean is filled with a repeating image of a circuit board (provides in Sun raster format). The text GMT in the center is an off-line PostScript file that was overlaid using psimage. The final panel repeats the top panel except that the land and sea images have changed places.

#!/bin/bash
#		GMT EXAMPLE 19
#		$Id$
#
# Purpose:	Illustrates various color pattern effects for maps
# GMT modules:	grdimage, grdmath, makecpt, pscoast, pstext, psimage
# Unix progs:	rm
#
ps=example_19.ps

# First make a worldmap with graded blue oceans and rainbow continents

gmt grdmath -Rd -I1 -r Y COSD 2 POW = lat.nc
gmt grdmath -Rd -I1 -r X = lon.nc
gmt makecpt -Cwhite,blue -T0,1 -Z -N > lat.cpt
gmt makecpt -Crainbow -T-180/180 > lon.cpt
gmt grdimage lat.nc -JI0/6.5i -Clat.cpt -P -K -Y7.5i -B0 -nl > $ps
gmt pscoast -R -J -O -K -Dc -A5000 -Gc >> $ps
gmt grdimage lon.nc -J -Clon.cpt -O -K -nl >> $ps
gmt pscoast -R -J -O -K -Q >> $ps
gmt pscoast -R -J -O -K -Dc -A5000 -Wthinnest >> $ps
echo "0 20 15TH INTERNATIONAL" | gmt pstext -R -J -O -K -F+f32p,Helvetica-Bold,red=thinner >> $ps
echo "0 -10 GMT CONFERENCE" | gmt pstext -R -J -O -K -F+f32p,Helvetica-Bold,red=thinner >> $ps
echo "0 -30 Honolulu, Hawaii, April 1, 2018" | gmt pstext -R -J -O -K \
	-F+f18p,Helvetica-Bold,green=thinnest >> $ps

# Then show example of color patterns and placing a PostScript image

gmt pscoast -R -J -O -K -Dc -A5000 -Gp86+fred+byellow+r100 -Spcircuit.ras+r100 -B0 -Y-3.25i >> $ps
echo "0 30 SILLY USES OF" | gmt pstext -R -J -O -K -F+f32p,Helvetica-Bold,lightgreen=thinner >> $ps
echo "0 -30 COLOR PATTERNS" | gmt pstext -R -J -O -K -F+f32p,Helvetica-Bold,magenta=thinner >> $ps
gmt psimage -DjCM+w3i -R -J GMT_covertext.eps -O -K >> $ps

# Finally repeat 1st plot but exchange the patterns

gmt grdimage lon.nc -J -Clon.cpt -O -K -Y-3.25i -B0 -nl >> $ps
gmt pscoast -R -J -O -K -Dc -A5000 -Gc >> $ps
gmt grdimage lat.nc -J -Clat.cpt -O -K -nl >> $ps
gmt pscoast -R -J -O -K -Q >> $ps
gmt pscoast -R -J -O -K -Dc -A5000 -Wthinnest >> $ps
echo "0 20 15TH INTERNATIONAL" | gmt pstext -R -J -O -K -F+f32p,Helvetica-Bold,red=thinner >> $ps
echo "0 -10 GMT CONFERENCE" | gmt pstext -R -J -O -K -F+f32p,Helvetica-Bold,red=thinner >> $ps
echo "0 -30 Honolulu, Hawaii, April 1, 2018" | gmt pstext -R -J -O \
	-F+f18p,Helvetica-Bold,green=thinnest >> $ps

rm -f l*.nc l*.cpt gmt.conf

Using color patterns and additional PostScript material in illustrations.