NAME

Math::Polygon::Clip - frame a polygon in a square

INHERITANCE

Math::Polygon::Clip
  is a Exporter

SYNOPSIS

my @poly  = ( [1,2], [2,4], [5,7], [1, 2] );
my @box   = ( $xmin, $ymin, $xmax, $ymax );

my $boxed = polygon_clip \@box, @poly;

DESCRIPTION

Cut-off all parts of the polygon which are outside the box

FUNCTIONS

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.

polygon_fill_clip2(ARRAY-BOX, LIST-OF-POINTS)

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).

polygon_fill_clip3(ARRAY-BOX, OUT-POLY, [IN-POLYS])

To be implemented. A surrounding polygon, with possible inclussions.

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]

SEE ALSO

This module is part of Math-Polygon distribution version 1.00, built on February 01, 2008. Website: http://perl.overmeer.net/geo/

LICENSE

Copyrights 2004,2006-2008 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 http://www.perl.com/perl/misc/Artistic.html