 Math::Polygon::Transform(3) 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

polygon_grid(%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.
polygon_mirror(%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.
polygon_move(%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.
polygon_resize(%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.
polygon_rotate(%options, LIST-of-\$points)
``` -Option --Default
center   [0,0]
degrees  0
```
center => POINT
degrees => FLOAT
specify rotation angle in degrees (between -180 and 360).
specify rotation angle in rads (between -pi and 2*pi)
polygon_simplify(%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'