Constructors

$obj->new(%options, [@points], %options)

Math::Polygon->new(%options, [@points], %options)

You may add %options before and/or after the @points. You may also use the "points" option to set the points. Each point in @points is (a references) to an ARRAY with two elements: an X and a Y coordinate.

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 anti-clockwise direction) will get copied unless overruled.

 -Option   --Default
  bbox       undef
  clockwise  undef
  points     undef
    

 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( [FORMAT] )

In LIST context, the points are returned as list, otherwise as reference to an ARRAY of points.

[1.09] When a FORMAT is given, each coordinate will get processed. This may be useful to hide platform specific rounding errors. FORMAT may be a CODE reference or a printf() alike string. See Math::Polygon::Calc::polygon_format().

example:

  my @points = $poly->points;
  my $first  = $points[0];
  my $x0 = $points[0][0];    # == $first->[0]  --> X
  my $y0 = $points[0][1];    # == $first->[1]  --> Y
  my @points = $poly->points("%.2f");
    

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 them. A new polygon is returned.

 -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 counter-clockwise 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 | \@points,[$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().

example:

  if($poly->equal($other_poly, 0.1)) ...
  if($poly->equal(\@points, 0.1)) ...
  if($poly->equal(@points)) ...
    

$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_polygon | \@points, [$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().

example:

  if($poly->same($other_poly, 0.1)) ...
  if($poly->same(\@points, 0.1)) ...
  if($poly->same(@points)) ...
    

$obj->startMinXY()

Returns a new polygon object, where the points are rotated in such a way that the point which is losest to the left-bottom point of the bounding box has become the first.

Function Math::Polygon::Calc::polygon_start_minxy().

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().

 -Option--Default
  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".

 -Option--Default
  b       0
  line    <undef>
  rc      undef
  x       undef
  y       undef
    

$obj->move(%options)

Returns a moved polygon object: all point are moved over the indicated distance. See Math::Polygon::Transform::polygon_move().

 -Option--Default
  dx      0
  dy      0
    

$obj->resize(%options)

Returns a resized polygon object. See Math::Polygon::Transform::polygon_resize().

 -Option--Default
  center  [0,0]
  scale   1.0
  xscale  <scale>
  yscale  <scale>
    

$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
    

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 ARRAYS-OF-POINTS containing line pieces from the input polygon. Function Math::Polygon::Clip::polygon_line_clip().

Display

$obj->string( [FORMAT] )

Print the polygon.

[1.09] When a FORMAT is specified, all coordinates will get formatted first. This may hide platform dependent rounding differences.