GD::Polygon - Polygon class for the GD image library

  http://www.cpan.org

package GD::Polygon;

use strict;
use Carp 'carp';
use GD;

# old documentation error
*GD::Polygon::delete = \&deletePt;

### The polygon object ###
# create a new polygon
sub new {
    my $class = shift;
    return bless { 'length'=>0,'points'=>[] },$class;
}

# automatic destruction of the polygon
sub DESTROY {
    my $self = shift;
    undef $self->{'points'};
}

sub clear {
  my $self = shift;
  $self->{'points'} = [];
}

# add an x,y vertex to the polygon
sub addPt {
    my($self,$x,$y) = @_;
    push(@{$self->{'points'}},[$x,$y]);
    $self->{'length'}++;
}

# get a vertex
sub getPt {
    my($self,$index) = @_;
    return () unless ($index>=0) && ($index<$self->{'length'});
    return @{$self->{'points'}->[$index]};
}

# change the value of a vertex
sub setPt {
    my($self,$index,$x,$y) = @_;
    unless (($index>=0) && ($index<$self->{'length'})) {
	carp "Attempt to set an undefined polygon vertex";
	return undef;
    }
    @{$self->{'points'}->[$index]} = ($x,$y);
    1;
}

# return the total number of vertices
sub length {
    my $self = shift;
    return $self->{'length'};
}

# return the array of vertices.
# each vertex is an two-member (x,y) array
sub vertices {
    my $self = shift;
    return @{$self->{'points'}};
}

# return the bounding box of the polygon
# (smallest rectangle that contains it)
sub bounds {
    my $self = shift;
    my($top,$bottom,$left,$right) = @_;
    $top =    99999999;
    $bottom =-99999999;
    $left =   99999999;
    $right = -99999999;
    my $v;
    foreach $v ($self->vertices) {
	$left = $v->[0] if $left > $v->[0];
	$right = $v->[0] if $right < $v->[0];
	$top = $v->[1] if $top > $v->[1];
	$bottom = $v->[1] if $bottom < $v->[1];
    }
    return ($left,$top,$right,$bottom);
}

# delete a vertex, returning it, just for fun
sub deletePt {
     my($self,$index) = @_;
     unless (($index>=0) && ($index<@{$self->{'points'}})) {
 	carp "Attempt to delete an undefined polygon vertex";
 	return undef;
     }
      my($vertex) = splice(@{$self->{'points'}},$index,1);
     $self->{'length'}--;
      return @$vertex;
  }

# translate the polygon in space by deltaX and deltaY
sub offset {
    my($self,$dh,$dv) = @_;
    my $size = $self->length;
    my($i);
    for ($i=0;$i<$size;$i++) {
	my($x,$y)=$self->getPt($i);
	$self->setPt($i,$x+$dh,$y+$dv);
    }
}

# map the polygon from sourceRect to destRect,
# translating and resizing it if necessary
sub map {
    my($self,$srcL,$srcT,$srcR,$srcB,$destL,$destT,$destR,$destB) = @_;
    my($factorV) = ($destB-$destT)/($srcB-$srcT);
    my($factorH) = ($destR-$destL)/($srcR-$srcL);
    my($vertices) = $self->length;
    my($i);
    for ($i=0;$i<$vertices;$i++) {
	my($x,$y) = $self->getPt($i);
	$x = int($destL + ($x - $srcL) * $factorH);
	$y = int($destT + ($y - $srcT) * $factorV);
	$self->setPt($i,$x,$y);
    }
}

# These routines added by Winfriend Koenig.
sub toPt {
    my($self, $dx, $dy) = @_;
    unless ($self->length > 0) {
	$self->addPt($dx,$dy);
	return;
    }
    my ($x, $y) = $self->getPt($self->length-1);
    $self->addPt($x+$dx,$y+$dy);
}

sub transform($$$$$$$) {
    # see PostScript Ref. page 154
    my($self, $a, $b, $c, $d, $tx, $ty) = @_;
    my $size = $self->length;
    for (my $i=0;$i<$size;$i++) {
	my($x,$y)=$self->getPt($i);
	$self->setPt($i, $a*$x+$c*$y+$tx, $b*$x+$d*$y+$ty);
    }
}

sub scale {
    my($self, $sx, $sy, $cx, $cy) = @_;
    $self->offset(-$cx,-$cy) if defined $cx or defined $cy;
    $self->transform($sx,0,0,$sy,$cx,$cy);
}

1;