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 Math::Polygon::Clip(3) User Contributed Perl Documentation Math::Polygon::Clip(3)

# NAME

Math::Polygon::Clip - frame a polygon in a square

# INHERITANCE

``` Math::Polygon::Clip
is a Exporter
```

# SYNOPSIS

``` my @poly  = ( [1,2], [2,4], [5,7], [1, 2] );
my @box   = ( \$xmin, \$ymin, \$xmax, \$ymax );
my \$boxed = polygon_clip \@box, @poly;
```

# DESCRIPTION

Cut-off all parts of the polygon which are outside the box

# FUNCTIONS

polygon_fill_clip1(\@box, @points)
Clipping a polygon into rectangles can be done in various ways. With this algorithm (which I designed myself, but may not be new), the parts of the polygon which are outside the @box are mapped on the borders. The polygon stays in one piece.
Returned is one list of points, which is cleaned from double points, spikes and superfluous intermediate points.
polygon_fill_clip2(\@box, @points)
To be implemented. The polygon falls apart in fragments, which are not connected: paths which are followed in two directions are removed. This is required by some applications, like polygons used in geographical context (country contours and such).
polygon_fill_clip3( \@box, \$out-\$poly, [\$in-\$polys] )
To be implemented. A surrounding polygon, with possible inclussions.
polygon_line_clip(\@box, @points)
Returned is a list of ARRAYS (possibly 0 long) containing line pieces from the input polygon (or line).
example:
``` my @points = ( [1,2], [2,3], [2,0], [1,-1], [1,2] );
my @bbox   = ( 0, -2, 2, 2 );
my @l      = polygon_line_clip \@bbox, @points;
print scalar @l;      # 1, only one piece found
my @first = @{\$l[0]}; # first is [2,0], [1,-1], [1,2]
```