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Manual Reference Pages  -  MATH::POLYGON::TRANSFORM (3)

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Math::Polygon::Transform - Polygon transformation



   is a Exporter


 my @poly = ( [1,2], [2,4], [5,7], [1, 2] );

 my $area = polygon_transform resize => 3.14, @poly;


This package contains polygon transformation algorithms.


<B>polygon_gridB>(%options, LIST-of-$points) Snap the polygon points to grid points, where artifacts are removed.

  raster  1.0

raster => FLOAT The raster size, which determines the points to round to. The origin [0,0] is always on a grid-point. When the raster value is zero, no transformation will take place.
<B>polygon_mirrorB>(%options, LIST-of-$points) Mirror the polygon in a line. Only one of the options can be provided. Some programs call this flip or flop.

  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 and b 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. The rc equals -dy/dx, the firing angle. If undef is explicitly specified then b is used as constant x: it’s a vertical mirror.
x => FLOAT Mirror in the line x=value, which means that y stays unchanged.
y => FLOAT Mirror in the line y=value, which means that x stays unchanged.
<B>polygon_moveB>(%options, LIST-of-$points) Returns a list of points which are moved over the indicated distance

  dx      0
  dy      0

dx => FLOAT Displacement in the horizontal direction.
dy => FLOAT Displacement in the vertical direction.
<B>polygon_resizeB>(%options, LIST-of-$points)

  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.
<B>polygon_rotateB>(%options, LIST-of-$points)

 -Option --Default
  center   [0,0]
  degrees  0
  radians  0

center => POINT
degrees => FLOAT specify rotation angle in degrees (between -180 and 360).
radians => FLOAT specify rotation angle in rads (between -pi and 2*pi)
<B>polygon_simplifyB>(%options, LIST-of-$points)

 -Option    --Default
  max_points  undef
  same        0.0001
  slope       undef

max_points => INTEGER First, same and slope 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.


Error: you need to specify ’x’, ’y’, ’rc’, or ’line’


This module is part of Math-Polygon distribution version 1.03, built on January 21, 2014. Website:


Copyrights 2004,2006-2014 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

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perl v5.20.3 MATH::POLYGON::TRANSFORM (3) 2014-01-21

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