NAME

       Math::Polygon::Calc - Simple polygon calculations

INHERITANCE

        Math::Polygon::Calc
          is an Exporter

SYNOPSIS

        my @poly = ( [1,2], [2,4], [5,7], [1, 2] );

        my ($xmin, $ymin, $xmax, $ymax) = polygon_bbox @poly;

        my $area = polygon_area @poly;
        MY $L    = polygon_perimeter @poly;
        if(polygon_is_clockwise @poly) { ... };

        my @rot  = polygon_start_minxy @poly;

DESCRIPTION

       This package contains a wide variaty of relatively easy polygon calculations.  More complex calculations
       are put in separate packages.

FUNCTIONS

       polygon_area(@points)
           Returns  the  area enclosed by the polygon.  The last point of the list must be the same as the first
           to produce a correct result.

           The algorithm was found at <http://mathworld.wolfram.com/PolygonArea.html>, and sounds:

            A = abs( 1/2 * (x1y2-x2y1 + x2y3-x3y2 ...)

       polygon_bbox(@points)
           Returns a list with four elements: (xmin, ymin, xmax, ymax), which describe the bounding box  of  the
           polygon (all points of the polygon are within that area.

       polygon_beautify( [\%options], @points )
           Polygons,  certainly  after some computations, can have a lot of horrible artifacts: points which are
           double, spikes, etc.  The optional HASH contains the %options.

            -Option       --Default
             remove_spikes  <false>

           remove_spikes => BOOLEAN
             Spikes contain of three successive points, where the first is on the line between  the  second  and
             the third.  The line goes from first to second, but then back to get to the third point.

             At the moment, only pure horizontal and pure vertical spikes are removed.

       polygon_centroid(@points)
           Returns the centroid location of the polygon.

           The  last  point  of  the  list must be the same as the first (must be 'closed') to produce a correct
           result.  When the polygon is very flat, it will not produce a stable result: minor changes in  single
           coordinates will move the centroid too far.

           The algorithm was found at http://en.wikipedia.org/wiki/Centroid#Of_a_polygon

       polygon_clockwise(@points)
           Be sure the polygon points are in clockwise order.

       polygon_contains_point($point, @points)
           Returns true if the point is inside the closed polygon.  On an edge will be flagged as 'inside'.  But
           be warned of rounding issues, caused by the floating-point calculations used by this algorithm.

       polygon_counter_clockwise(@points)
           Be sure the polygon points are in counter-clockwise order.

       polygon_distance($point, @polygon)
           [1.05] calculate the shortest distance between a point and any vertex of a closed polygon.

       polygon_equal( \@points1, \@points2, [$tolerance] )
           Compare  two  polygons, on the level of points. When the polygons are the same but rotated, this will
           return false. See polygon_same().

       polygon_format($format, @points)
           [1.07] Map the $format over all @points, both the X and Y coordinate.  This is especially  useful  to
           reduce the number of digits in the stringification.  For instance, when you want reproducible results
           in regression scripts.

           The  format  is  anything  supported  by  printf(),  for  instance  "%5.2f".  Or, you can pass a code
           reference which accepts a single value.

       polygon_is_clockwise(@points)
       polygon_is_closed(@points)
       polygon_perimeter(@points)
           The length of the line of the polygon.  This can also be used to compute the length of any  line:  of
           the last point is not equal to the first, then a line is presumed; for a polygon they must match.

           This is simply Pythagoras.

            $l = sqrt((x1-x0)^2 + (y1-y0)^2) + sqrt((x2-x1)^2+(y2-y1)^2) + ...

       polygon_same( \@points1, \@points2, [$tolerance] )
           Compare  two  polygons,  where the polygons may be rotated wrt each other. This is (much) slower than
           polygon_equal(), but some algorithms will cause un unpredictable rotation in the result.

       polygon_start_minxy(@points)
           Returns the polygon, where the point which is closest to the left-bottom corner of the  bounding  box
           is made first.

       polygon_string(@points)

SEE ALSO

       This  module  is  part  of  Math-Polygon  distribution  version  1.11,  built  on  May 02, 2025. Website:
       http://perl.overmeer.net/CPAN/

LICENSE

       Copyrights 2004-2025 by [Mark Overmeer <markov@cpan.org>]. 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://dev.perl.org/licenses/

perl v5.40.1                                       2025-05-16                           Math::Polygon::Calc(3pm)