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# This code is part of Perl distribution Math-Polygon version 2.00.
# The POD got stripped from this file by OODoc version 3.03.
# For contributors see file ChangeLog.
# This software is copyright (c) 2004-2025 by Mark Overmeer.
# This is free software; you can redistribute it and/or modify it under
# the same terms as the Perl 5 programming language system itself.
# SPDX-License-Identifier: Artistic-1.0-Perl OR GPL-1.0-or-later
#oodist: *** DO NOT USE THIS VERSION FOR PRODUCTION ***
#oodist: This file contains OODoc-style documentation which will get stripped
#oodist: during its release in the distribution. You can use this file for
#oodist: testing, however the code of this development version may be broken!
package Math::Polygon::Clip;{
our $VERSION = '2.00';
}
use parent 'Exporter';
use strict;
use warnings;
our @EXPORT = qw/
polygon_line_clip
polygon_fill_clip1
/;
use Log::Report 'math-polygon';
use List::Util qw/min max/;
use Math::Polygon::Calc;
sub _inside($$);
sub _cross($$$);
sub _cross_inside($$$);
sub _cross_x($$$);
sub _cross_y($$$);
sub _remove_doubles(@);
#--------------------
sub polygon_fill_clip1($@)
{ my $bbox = shift;
my ($xmin, $ymin, $xmax, $ymax) = @$bbox;
@_ or return (); # empty list of points
# Collect all crosspoints with axes, plus the original points
my $next = shift;
my @poly = $next;
while(@_)
{ $next = shift;
push @poly, _cross($bbox, $poly[-1], $next), $next;
}
# crop them to the borders: outside is projected on the sides
my @cropped;
foreach (@poly)
{ my ($x,$y) = @$_;
$x = $xmin if $x < $xmin;
$x = $xmax if $x > $xmax;
$y = $ymin if $y < $ymin;
$y = $ymax if $y > $ymax;
push @cropped, [$x, $y];
}
polygon_beautify +{despike => 1}, @cropped;
}
sub polygon_line_clip($@)
{ my $bbox = shift;
my ($xmin, $ymin, $xmax, $ymax) = @$bbox;
my @frags;
my $from = shift;
my $fromin = _inside $bbox, $from;
push @frags, [ $from ] if $fromin;
while(@_)
{ my $next = shift;
my $nextin = _inside $bbox, $next;
if($fromin && $nextin) # stay within
{ push @{$frags[-1]}, $next;
}
elsif($fromin && !$nextin) # leaving
{ push @{$frags[-1]}, _cross_inside $bbox, $from, $next;
}
elsif($nextin) # entering
{ my @cross = _cross_inside $bbox, $from, $next;
push @frags, [ @cross, $next ];
}
else # pass thru bbox?
{ my @cross = _cross_inside $bbox, $from, $next;
push @frags, \@cross if @cross;
}
($from, $fromin) = ($next, $nextin);
}
# Glue last to first?
if( @frags >= 2
&& $frags[0][0][0] == $frags[-1][-1][0] # X
&& $frags[0][0][1] == $frags[-1][-1][1] # Y
)
{ my $last = pop @frags;
pop @$last;
unshift @{$frags[0]}, @$last;
}
@frags;
}
#
### Some helper functions
#
sub _inside($$)
{ my ($bbox, $point) = @_;
$bbox->[0] <= $point->[0]+0.00001
&& $point->[0] <= $bbox->[2]+0.00001 # X
&& $bbox->[1] <= $point->[1]+0.00001
&& $point->[1] <= $bbox->[3]+0.00001; # Y
}
sub _sector($$) # left-top 678,345,012 right-bottom
{ my ($bbox, $point) = @_;
my $xsector = $point->[0] < $bbox->[0] ? 0
: $point->[0] < $bbox->[2] ? 1
: 2;
my $ysector = $point->[1] < $bbox->[1] ? 0
: $point->[1] < $bbox->[3] ? 1
: 2;
$ysector * 3 + $xsector;
}
sub _cross($$$)
{ my ($bbox, $from, $to) = @_;
my ($xmin, $ymin, $xmax, $ymax) = @$bbox;
my @cross = (
_cross_x($xmin, $from, $to),
_cross_x($xmax, $from, $to),
_cross_y($ymin, $from, $to),
_cross_y($ymax, $from, $to),
);
# order the results
$from->[0] < $to->[0] ? sort({$a->[0] <=> $b->[0]} @cross)
: $from->[0] > $to->[0] ? sort({$b->[0] <=> $a->[0]} @cross)
: $from->[1] < $to->[1] ? sort({$a->[1] <=> $b->[1]} @cross)
: sort({$b->[1] <=> $a->[1]} @cross);
}
sub _cross_inside($$$)
{ my ($bbox, $from, $to) = @_;
grep _inside($bbox, $_), _cross($bbox, $from, $to);
}
sub _remove_doubles(@)
{ my $this = shift or return ();
my @ret = $this;
while(@_)
{ my $this = shift;
next if $this->[0]==$ret[-1][0] && $this->[1]==$ret[-1][1];
push @ret, $this;
}
@ret;
}
sub _cross_x($$$)
{ my ($x, $from, $to) = @_;
my ($fx, $fy) = @$from;
my ($tx, $ty) = @$to;
return () unless $fx < $x && $x < $tx || $tx < $x && $x < $fx;
my $y = $fy + ($x - $fx)/($tx - $fx) * ($ty - $fy);
(($fy <= $y && $y <= $ty) || ($ty <= $y && $y <= $fy)) ? [$x,$y] : ();
}
sub _cross_y($$$)
{ my ($y, $from, $to) = @_;
my ($fx, $fy) = @$from;
my ($tx, $ty) = @$to;
return () unless $fy < $y && $y < $ty || $ty < $y && $y < $fy;
my $x = $fx + ($y - $fy)/($ty - $fy) * ($tx - $fx);
(($fx <= $x && $x <= $tx) || ($tx <= $x && $x <= $fx)) ? [$x,$y] : ();
}
1;
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