#!/bin/bash

for i
do
    case $i in
	arc=*)
	    arc=${i#arc=}
	    ;;
	azi*=*)
	    azimuth=${i#azi*=}
	    ;;
	map=*)
	    map=${i#map=}
	    ;;
	coord*=*)
	    coord=${i#coord*=} 
	    x=${coord%,*} 
	    y=${coord#*,}
	    ;;
    esac
done

if [ ! "$arc" -o ! "$azimuth" -o ! "$map" -o ! "$x" -o ! "$y" ];
then
    echo "Usage: $(basename $0)"
    echo "    map=raster coordinates=x,y arc=value azimuth=value"
    exit -1
fi

r.mapcalc <<EOF
$map = eval( \\
    min   = $azimuth - ($arc / 2), \\
    max   = $azimuth + ($arc / 2), \\
    theta = atan( y() - $y, x() - $x ), \\
    if( \\
	((theta >= min) && (theta <= max)) || \\
	((theta - 360 >= min) && (theta - 360 <= max)), \\
	1, 0 ) \\
)
EOF

r.colors map=$map color=rules <<EOF
0 black
1 white
EOF