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Mark Overmeer
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# NAME

Math::Polygon::Surface - Polygon with exclusions

# SYNOPSIS

`````` my \$outer   = Math::Polygon->new( [1,2], [2,4], [5,7], [1,2] );
my \$surface = Math::Polygon::Surface->new(\$outer);``````

# DESCRIPTION

A surface is one polygon which represents the outer bounds of an array, plus optionally a list of polygons which represent exclusions from that outer polygon.

# METHODS

## Constructors

\$obj->new( [%options], [@polygons], %options )
Math::Polygon::Surface->new( [%options], [@polygons], %options )

You may merge %options with @polygons. You may also use the "outer" and "inner" options.

Each polygon is a references to an ARRAY of points, each an ARRAY of X and Y, but better pass Math::Polygon objects.

`````` -Option--Default
inner   []
outer   undef``````
inner => \@polygons

The inner polygons, zero or more Math::Polygon objects.

outer => \$polygon

The outer polygon, a Math::Polygon.

## Attributes

\$obj->inner()

Returns a list (often empty) of inner polygons.

\$obj->outer()

Returns the outer polygon.

## Simple calculations

area()

Returns the area enclosed by the outer polygon, minus the areas of the inner polygons. See method Math::Polygon::area().

\$obj->bbox()

Returns a list with four elements: (xmin, ymin, xmax, ymax), which describe the bounding box of the surface, which is the bbox of the outer polygon. See method Math::Polygon::bbox().

\$obj->perimeter()

The length of the border: sums outer and inner perimeters. See method Math::Polygon::perimeter().

## Clipping

\$obj->fillClip1(\$box)

Clipping a polygon into rectangles can be done in various ways. With this algorithm, the parts of the polygon which are outside the \$box are mapped on the borders.

All polygons are treated separately.

\$obj->lineClip(\$box)

Returned is a list of ARRAYS-OF-POINTS containing line pieces from the input surface. Lines from outer and inner polygons are undistinguishable. See method Math::Polygon::lineClip().

\$obj->string()

Translate the surface structure into some string. Use Geo::WKT if you need a standardized format.

Returned is a single string possibly containing multiple lines. The first line is the outer, the other lines represent the inner polygons.

# DIAGNOSTICS

Error: surface requires outer polygon