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

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
 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)

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'

SEE ALSO

This module is part of Math-Polygon distribution version 1.02, built on September 19, 2011. Website: http://perl.overmeer.net/geo/

LICENSE

Copyrights 2004,2006-2011 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 http://www.perl.com/perl/misc/Artistic.html