Shape Files

Below is a perl script to create a PNG from a Shape file.
use strict;
use warnings;

use GD;
GD::Image->trueColor(1);

my $width = 8 * 1024;
my $height = 8 * 1024;

my $shpfile = $ARGV[0];
open(FH, "<$shpfile") or die("No input file\n");
binmode(FH); 

my $csvfile = $shpfile;
$csvfile =~ s/.shp$/.csv/g;
open(POLYOUT, ">$csvfile");

my $buffer;
my $num_bytes = read(FH, $buffer, 100);
my ($code, $u1, $u2, $u3, $u4, $u5, $filelength, $version, $type, $BBminX, $BBminY, $BBmaxX, $BBmaxY, $BBminZ, $BBmaxZ, $BBminM, $BBmaxM) = unpack("N N N N N N N V V F F F F F F F F", $buffer);
print "code = $code\n";
print "filelength = $filelength\n";
print "version = $version\n";
print "minX = $BBminX\n";
print "minY = $BBminY\n";
print "maxX = $BBmaxX\n";
print "maxY = $BBmaxY\n";
print "minZ = $BBminZ\n";
print "maxZ = $BBmaxZ\n";
print "minM = $BBminM\n";
print "maxM = $BBmaxM\n";

sub mapx {
    my $x = shift;
    return ($x - $BBminX) / ($BBmaxX - $BBminX) * $width;
}

sub mapy {
    my $y = shift;
    return $height - ($y - $BBminY) / ($BBmaxY - $BBminY) * $height;
}

my $polyCount = 0;

my $img = new GD::Image($width, $height);

while (read(FH, $buffer, 12)) {
    my ($recordnumber, $recordlength, $shapetype) = unpack("N N V", $buffer);
    if ($shapetype == 5) {
        # Polygon
        read(FH, $buffer, 4 * 8 + 2 * 4);
        my ($minX, $minY, $maxX, $maxY, $NumParts, $NumPoints) = unpack("F F F F V V", $buffer);
        my @parts;
        foreach my $part (1 .. $NumParts) {
            read(FH, $buffer, 4);
            my ($part) = unpack("V", $buffer);
            push @parts, $part;
            #syswrite(SHPOUT, pack("V", $part), 4);
        }
        push @parts, $NumPoints;
        @parts = reverse @parts;
        while (@parts) {
            my $firstpoint = pop @parts;
            my $lastpoint = pop @parts;
            my $poly = new GD::Polygon;
            $polyCount++;
            foreach ($firstpoint .. $lastpoint - 1) {
                read(FH, $buffer, 16);
                my ($x, $y) = unpack("F F", $buffer);
                print POLYOUT "$x,$y,$polyCount\n";
                $poly->addPt(mapx($x), mapy($y));
            }
            $img->openPolygon($poly, 0xff0000);
            push @parts, $lastpoint if (@parts);
        }
    } elsif ($shapetype == 3) {
        # PolyLine
        read(FH, $buffer, 4 * 8 + 2 * 4);
        my ($minX, $minY, $maxX, $maxY, $NumParts, $NumPoints) = unpack("F F F F V V", $buffer);
        my @parts;
        foreach my $part (1 .. $NumParts) {
            read(FH, $buffer, 4);
            my ($part) = unpack("V", $buffer);
            push @parts, $part;
        }
        push @parts, $NumPoints;
        @parts = reverse @parts;
        while (@parts) {
            my $firstpoint = pop @parts;
            my $lastpoint = pop @parts;
            read(FH, $buffer, 16);
            my ($x1, $y1) = unpack("F F", $buffer);
            print POLYOUT "$x1,$y1\n";
            foreach ($firstpoint .. $lastpoint - 2) {
                read(FH, $buffer, 16);
                my ($x2, $y2) = unpack("F F", $buffer);
                print POLYOUT "$x2,$y2\n";
                $img->line(mapx($x1), mapy($y1), mapx($x2), mapy($y2), 0xff0000);
                $x1 = $x2;
                $y1 = $y2;
            }
            push @parts, $lastpoint if (@parts);
        }

    } elsif ($shapetype == 1) {
        read(FH, $buffer, 2 * 8);
        my ($x, $y) = unpack("F F", $buffer);
        $img->setPixel(mapx($x), mapy($y), 0xff0000);
        print POLYOUT "$x,$y\n";
    } else {
        print "unhandled type shapetype = $shapetype\n";
        read(FH, $buffer, $recordlength * 2 - 4);
    }
}

close(POLYOUT);

my $pngfile = $shpfile;
$pngfile =~ s/.shp$/.png/g;
open(PNGOUT, ">$pngfile");
binmode(PNGOUT);
print PNGOUT $img->png;
close(PNGOUT);
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