NAME
Math::Polygon  Class for maintaining polygon data
SYNOPSIS
my $poly = Math::Polygon>new( [1,2], [2,4], [5,7], [1,2] );
print $poly>nrPoints;
my @p = $poly>points;
my ($xmin, $ymin, $xmax, $ymax) = $poly>bbox;
my $area = $poly>area;
my $l = $poly>perimeter;
if($poly>isClockwise) { ... };
my $rot = $poly>startMinXY;
my $center = $poly>centroid;
if($poly>contains($point)) { ... };
my $boxed = $poly>lineClip($xmin, $xmax, $ymin, $ymax);
DESCRIPTION
This class provides an OO interface around Math::Polygon::Calc and Math::Polygon::Clip.
METHODS
Constructors
 $obj>new( [%options], [@points], [%options] )
 Math::Polygon>new( [%options], [@points], [%options] )

You may add %options after and/or before the $points. You may also use the "points" options to get the points listed. $points are references to an ARRAY of X and Y.
When
new
is called as instance method, it is believed that the new polygon is derived from the callee, and therefore some facts (like clockwise or anticlockwise direction) will get copied unless overruled.Option Default bbox undef clockwise undef points undef
 bbox => ARRAY

Usually computed from the figure automatically, but can also be specified as [xmin,ymin,xmax, ymax]. See bbox().
 clockwise => BOOLEAN

Is not specified, it will be computed by the isClockwise() method on demand.
 points => ARRAYofPOINTS

See points() and nrPoints().
example: creation of new polygon
my $p = Math::Polygon>new([1,0],[1,1],[0,1],[0,0],[1,0]); my @p = ([1,0],[1,1],[0,1],[0,0],[1,0]); my $p = Math::Polygon>new(points => \@p);
Attributes
 $obj>nrPoints()

Returns the number of points,
 $obj>order()

Returns the number of unique points: one less than nrPoints().
 $obj>point( $index, [$index,...] )

Returns the point with the specified $index or INDEXES. In SCALAR context, only the first $index is used.
example:
my $point = $poly>point(2); my ($first, $last) = $poly>point(0, 1);
 $obj>points()

In LIST context, the points are returned as list, otherwise as reference to an ARRAY.
example:
my @points = $poly>points; my $first = $points[0]; my $x0 = $points[0][0]; # $first>[0] my $y0 = $points[0][1]; # $first>[1]
Geometry
 $obj>area()

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 computed result is cached. Function Math::Polygon::Calc::polygon_area().
example:
my $area = $poly>area; print "$area $poly_units ^2\n";
 $obj>bbox()

Returns a list with four elements: (xmin, ymin, xmax, ymax), which describe the bounding box of the polygon (all points of the polygon are inside that area). The computation is expensive, and therefore, the results are cached. Function Math::Polygon::Calc::polygon_bbox().
example:
my ($xmin, $ymin, $xmax, $ymax) = $poly>bbox;
 $obj>beautify(%options)

Returns a new, beautified version of this polygon. Function Math::Polygon::Calc::polygon_beautify().
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
Option Default remove_spikes <false>
 $obj>centroid()

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 computed result is cached. Function Math::Polygon::Calc::polygon_centroid().
example:
my $center = $poly>centroid; my ($cx, $cy) = @$center;
 $obj>clockwise()

Make sure the points are in clockwise order.
example:
$poly>clockwise;
 $obj>contains($point)

Returns a truth value indicating whether the point is inside the polygon or not. On the edge is inside.
 $obj>counterClockwise()

Make sure the points are in counterclockwise order.
example:
$poly>counterClockwise
 $obj>distance(POINT)

[1.05] Returns the distance of the point to the closest point on the border of the polygon, zero if the point is on an edge.
 $obj>equal( <$other  ARRAY,[$tolerance]>  $points )

Compare two polygons, on the level of points. When the polygons are the same but rotated, this will return false. See same(). Function Math::Polygon::Calc::polygon_equal().
 $obj>isClockwise()

The points are (in majority) orded in the direction of the hands of the clock. This calculation is quite expensive (same effort as calculating the area of the polygon), and the result is therefore cached.
example:
if($poly>isClockwise) ...
 $obj>isClosed()

Returns true if the first point of the poly definition is the same as the last point.
 $obj>perimeter()

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. Function Math::Polygon::Calc::polygon_perimeter().
example:
my $fence = $poly>perimeter; print "fence length: $fence $poly_units\n"
 $obj>same( <$other  ARRAY,[$tolerance]>  $points )

Compare two polygons, where the polygons may be rotated wrt each other. This is (much) slower than equal(), but some algorithms will cause un unpredictable rotation in the result. Function Math::Polygon::Calc::polygon_same().
 $obj>startMinXY()

Returns a new polygon object, where the points are rotated in such a way that the point which is losest to the leftbottom point of the bounding box has become the first.
Transformations
Implemented in Math::Polygon::Transform: changes on the structure of the polygon except clipping. All functions return a new polygon object or undef.
 $obj>grid(%options)

Returns a polygon object with the points snapped to grid points. See Math::Polygon::Transform::polygon_grid().
OptionDefault raster 1.0
 $obj>mirror(%options)

Mirror the polygon in a line. Only one of the options can be provided. Some programs call this "flip" or "flop".
OptionDefault b 0 line <undef> rc undef x undef y undef
 b => FLOAT

Only used in combination with option
rc
to describe a line.  line => [POINT, POINT]

Alternative way to specify the mirror line. The
rc
andb
are computed from the two points of the line.  rc => FLOAT

Description of the line which is used to mirror in. The line is
y= rc*x+b
. Therc
equalsdy/dx
, the firing angle. Ifundef
is explicitly specified thenb
is used as constant x: it's a vertical mirror.  x => FLOAT

Mirror in the line
x=value
, which means thaty
stays unchanged.  y => FLOAT

Mirror in the line
y=value
, which means thatx
stays unchanged.
 $obj>move(%options)

Returns a moved polygon object: all point are moved over the indicated distance. See Math::Polygon::Transform::polygon_move().
OptionDefault dx 0 dy 0
 $obj>resize(%options)

Returns a resized polygon object. See Math::Polygon::Transform::polygon_resize().
OptionDefault center [0,0] scale 1.0 xscale <scale> yscale <scale>
 center => POINT
 scale => FLOAT

Resize the polygon with the indicated factor. When the factor is larger than 1, the resulting polygon with grow, when small it will be reduced in size. The scale will be respective from the center.
 xscale => FLOAT

Specific scaling factor in the horizontal direction.
 yscale => FLOAT

Specific scaling factor in the vertical direction.
 $obj>rotate(%options)

Returns a rotated polygon object: all point are moved over the indicated distance. See Math::Polygon::Transform::polygon_rotate().
Option Default center [0,0] degrees 0 radians 0
 $obj>simplify(%options)

Returns a polygon object where points are removed. See Math::Polygon::Transform::polygon_simplify().
Option Default max_points undef same 0.0001 slope undef
 max_points => INTEGER

First,
same
andslope
reduce the number of points. Then, if there are still more than the specified number of points left, the points with the widest angles will be removed until the specified maximum number is reached.  same => FLOAT

The distance between two points to be considered "the same" point. The value is used as radius of the circle.
 slope => FLOAT

With three points X(n),X(n+1),X(n+2), the point X(n+1) will be removed if the length of the path over all three points is less than
slope
longer than the direct path between X(n) and X(n+2).The slope will not be removed around the starting point of the polygon. Removing points will change the area of the polygon.
Clipping
 $obj>fillClip1($box)

Clipping a polygon into rectangles can be done in various ways. With this algorithm, the parts of the polygon which are outside the $box are mapped on the borders. The polygon stays in one piece, but may have vertices which are followed in two directions.
Returned is one polygon, which is cleaned from double points, spikes and superfluous intermediate points, or
undef
when no polygon is outside the $box. Function Math::Polygon::Clip::polygon_fill_clip1().  $obj>lineClip($box)

Returned is a list of ARRAYSOFPOINTS containing line pieces from the input polygon. Function Math::Polygon::Clip::polygon_line_clip().
Display
SEE ALSO
This module is part of MathPolygon distribution version 1.06, built on July 16, 2017. Website: http://perl.overmeer.net/geo/
LICENSE
Copyrights 20042017 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/