``````=encoding utf8

Math::Polygon::Transform - Polygon transformation

Math::Polygon::Transform
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.

=over 4

=item B<polygon_grid>(%options, @points)

Snap the polygon points to grid points, where artifacts are removed.

-Option--Default
raster  1.0

=over 2

=item raster => FLOAT

The raster size, which determines the points to round to.  The origin
C<[0,0]> is always on a grid-point.  When the raster value is zero,
no transformation will take place.

=back

=item B<polygon_mirror>(%options, @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

=over 2

=item b => FLOAT

Only used in combination with option C<rc> to describe a line.

=item line => [POINT, POINT]

Alternative way to specify the mirror line.  The C<rc> and C<b> are
computed from the two points of the line.

=item rc => FLOAT

Description of the line which is used to mirror in. The line is
C<y= rc*x+b>.  The C<rc> equals C<-dy/dx>, the firing angle.  If
C<undef> is explicitly specified then C<b> is used as constant x: it's
a vertical mirror.

=item x => FLOAT

Mirror in the line C<x=value>, which means that C<y> stays unchanged.

=item y => FLOAT

Mirror in the line C<y=value>, which means that C<x> stays unchanged.

=back

=item B<polygon_move>(%options, @points)

Returns a list of points which are moved over the indicated distance

-Option--Default
dx      0
dy      0

=over 2

=item dx => FLOAT

Displacement in the horizontal direction.

=item dy => FLOAT

Displacement in the vertical direction.

=back

=item B<polygon_resize>(%options, @points)

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

=over 2

=item center => POINT

=item 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.

=item xscale => FLOAT

Specific scaling factor in the horizontal direction.

=item yscale => FLOAT

Specific scaling factor in the vertical direction.

=back

=item B<polygon_rotate>(%options, @points)

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

=over 2

=item center => POINT

=item degrees => FLOAT

specify rotation angle in degrees (between -180 and 360).

specify rotation angle in rads (between -pi and 2*pi)

=back

=item B<polygon_simplify>(%options, @points)

-Option    --Default
max_points  undef
same        0.0001
slope       undef

=over 2

=item max_points => INTEGER

First, C<same> and C<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.

=item same => FLOAT

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

=item 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 C<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.

=back

=back

=over 4

=item Error: you need to specify 'x', 'y', 'rc', or 'line'

=back