NAME

       Math::Polygon::Calc - Simple polygon calculations

INHERITANCE

        Math::Polygon::Calc
          is a 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(LIST-OF-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(LIST-OF-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([HASH], LIST-OF-POINTS)
           Polygons, certainly after some computations, can have a lot of horrible artifacts:
           points which are double, spikes, etc.  This functions provided by this module beautify
           The optional HASH contains the OPTIONS:

            -Option        --Default
             remove_between  <false>
             remove_spikes   <false>

           remove_between => BOOLEAN
             Simple points in-between are always removed, but more complex points are not: when
             the line is not parallel to one of the axes, more intensive calculations must take
             place.  This will only be done when this flags is set.  NOT IMPLEMENTED YET

           remove_spikes => BOOLEAN
       polygon_centroid(LIST-OF-POINTS)
           Returns the centroid location of 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://en.wikipedia.org/wiki/Centroid#Centroid_of_polygon

       polygon_clockwise(LIST-OF-POINTS)
           Be sure the polygon points are in clockwise order.

       polygon_contains_point(POINT, LIST-OF-POINTS)
           Returns true if the point is unside the closed polygon.

       polygon_counter_clockwise(LIST-OF-POINTS)
           Be sure the polygon points are in counter-clockwise order.

       polygon_equal(ARRAY-OF-POINTS, ARRAY-OF-POINTS, [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_is_clockwise(LIST-OF-POINTS)
       polygon_is_closed(POINTS)
       polygon_perimeter(LIST-OF-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(ARRAY-OF-POINTS, ARRAY-OF-POINTS, [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(LIST-OF-POINTS)
           Returns the polygon, where the point which is closest to the left-bottom corner of the
           bounding box is made first.

       polygon_string(LIST-OF-POINTS)

SEE ALSO

       This module is part of Math-Polygon distribution version 1.02, built on September 19,
       2011. Website: http://perl.overmeer.net/geo/

LICENSE

       Copyrights 2004,2006-2011 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