/usr/share/perl5/Math/Polygon/Clip.pod is in libmath-polygon-perl 1.03-1.
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=head1 NAME
Math::Polygon::Clip - frame a polygon in a square
=head1 INHERITANCE
Math::Polygon::Clip
is a Exporter
=head1 SYNOPSIS
my @poly = ( [1,2], [2,4], [5,7], [1, 2] );
my @box = ( $xmin, $ymin, $xmax, $ymax );
my $boxed = polygon_clip \@box, @poly;
=head1 DESCRIPTION
Cut-off all parts of the polygon which are outside the box
=head1 FUNCTIONS
=over 4
=item B<polygon_fill_clip1>(ARRAY-$box, LIST-of-$points)
Clipping a polygon into rectangles can be done in various ways.
With this algorithm (which I designed myself, but may not be new), the
parts of the polygon which are outside the $box are mapped on the borders.
The polygon stays in one piece.
Returned is one list of points, which is cleaned from double points,
spikes and superfluous intermediate points.
=item B<polygon_fill_clip2>(ARRAY-$box, LIST-of-$points)
B<To be implemented>. The polygon falls apart in fragments, which are not
connected: paths which are followed in two directions are removed.
This is required by some applications, like polygons used in geographical
context (country contours and such).
=item B<polygon_fill_clip3>(ARRAY-$box, $out-$poly, [$in-$polys])
B<To be implemented>. A surrounding polygon, with possible
inclussions.
=item B<polygon_line_clip>(ARRAY-$box, LIST-of-$points)
Returned is a list of ARRAYS (possibly 0 long) containing line pieces
from the input polygon (or line).
example:
my @points = ( [1,2], [2,3], [2,0], [1,-1], [1,2] );
my @bbox = ( 0, -2, 2, 2 );
my @l = polygon_line_clip \@bbox, @points;
print scalar @l; # 1, only one piece found
my @first = @{$l[0]}; # first is [2,0], [1,-1], [1,2]
=back
=head1 SEE ALSO
This module is part of Math-Polygon distribution version 1.03,
built on January 21, 2014. Website: F<http://perl.overmeer.net/geo/>
=head1 LICENSE
Copyrights 2004,2006-2014 by [Mark Overmeer]. For other contributors see ChangeLog.
This program is free software; you can redistribute it and/or modify it
under the same terms as Perl itself.
See F<http://www.perl.com/perl/misc/Artistic.html>
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