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(@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 to produce a correct result.

           The algorithm was found at http://en.wikipedia.org/wiki/Centroid#Centroid_of_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 1.10, built on January 03, 2018.
       Website: http://perl.overmeer.net/CPAN/

LICENSE

       Copyrights 2004-2018 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://dev.perl.org/licenses/