Listing 6 Overlaying the UC icons on the cropped image 

# Load the icon file
#
use constant ICON_FILE => 'icon.png';

my $fh = new FileHandle( ICON_FILE );
unless ($fh) { die "Cannot open UC icon file ", ICON_FILE; }

flock( $fh, LOCK_SH );

$ImgIcon = GD::Image->newFromPng( $fh );

flock( $fh, LOCK_UN );
close( $fh );

# Make sure icon's yellow is in pallette!
#
$ImgCrop->colorAllocate(255, 222, 0);

my ($x_left, $y_top, $x_right, $y_bottom) =
   getZoomedInCoords( getImageMapCoords() );

my @Locations = getIconLocationsByCoords($x_left, $y_top, $x_right, $y_bottom);

# For each returned project location overlay a UC icon on the map.
# (Note that we do not check to see if icons overlap, because of the
# way we store location infromation in the Map table.)
# 
foreach my $ref ( @Locations ) {
   $ImgCrop->copy( $ImgIcon,
 	       	 $ref->{X} - $x_left - HALF_ICON,
 	       	 $ref->{Y} - $y_top  - HALF_ICON,
 	       	 0, 0, ICON_DIM, ICON_DIM );
}

