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 1.03, built on January 21, 2014. Website: http://perl.overmeer.net/geo/

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 http://www.perl.com/perl/misc/Artistic.html