#!/bin/sh
convert -compress none -resize 66x23 - pgm:- |
perl -e '
<> eq "P2\n" or die "ascii pgm input required\n";
<>; <>;  # ignore depth, dimensions

my @ch = split //, " .oO@";
while (<>) {
	print $ch[ $_ * @ch >> 8 ] for /\d+/g;
	print $/;
}
'