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

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NAME

Math::Polygon::Transform - Polygon transformation

INHERITANCE

```

Math::Polygon::Transform
is a Exporter

```

SYNOPSIS

```

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

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

```

DESCRIPTION

This package contains polygon transformation algorithms.

FUNCTIONS

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

```

-Option--Default
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.

```

-Option--Default
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

```

-Option--Default
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)
```

-Option--Default
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

```
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.

DIAGNOSTICS

 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: http://perl.overmeer.net/geo/