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