Algorithm::Line::Bresenham - simple pixellated line-drawing algorithm
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NAME
Algorithm::Line::Bresenham - simple pixellated line-drawing algorithm
SYNOPSIS
use Algorithm::Line::Bresenham qw/line/;
my @points = line(3,3 => 5,0);
# returns the list: [3,3], [4,2], [4,1], [5,0]
line(3,3 => 5,0, \&draw_line);
# calls draw_line on each point in turn
DESCRIPTION
Bresenham is one of the canonical line drawing algorithms for pixellated grids.
Given a start and an end-point, Bresenham calculates which points on the grid
need to be filled to generate the line between them.
Googling for 'Bresenham', and 'line drawing algorithms' gives some good
overview. The code here takes its starting point from Mark Feldman's Pascal
code in his article Bresenham's Line and Circle Algorithms at
http://www.gamedev.net/reference/articles/article767.asp.
FUNCTIONS
line
line ($from_y, $from_x => $to_y, $to_x);
Generates a list of all the intermediate points. This is returned as a list
of array references.
line ($from_y, $from_x => $to_y, $to_x, \&callback);
Calls the referenced function on each point in turn. The callback could be
used to actually draw the point. Returns the collated return values from the
callback.
circle
my @points = circle ($y, $x, $radius)
Returns the points to draw a circle with
TODO and BUGS
THANKS
Patches for the circle algorithm and a float value bug contributed by Richard Clamp, thanks!
AUTHOR and LICENSE
osfameron, osfameron@cpan.org
Copyright (c) 2004-2006 osfameron. All rights reserved.
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
package Algorithm::Line::Bresenham;
use strict; use warnings;
our $VERSION = 0.11;
use base 'Exporter';
our @EXPORT_OK = qw/line circle/;
sub line {
my ($from_y, $from_x, $to_y, $to_x, $callback) = @_;
$_ = int $_ for ($from_y, $from_x, $to_y, $to_x);
my ($delta_y, $delta_x) = ($to_y-$from_y, $to_x-$from_x);
my $dir = abs($delta_y) > abs($delta_x);
my ($curr_maj, $curr_min, $to_maj, $to_min, $delta_maj, $delta_min) =
$dir ?
($from_y, $from_x, $to_y, $to_x, $delta_y, $delta_x)
: ($from_x, $from_y, $to_x, $to_y, $delta_x, $delta_y);
my $inc_maj = sig($delta_maj);
my $inc_min = sig($delta_min);
($delta_maj, $delta_min) = (abs($delta_maj)+0, abs($delta_min)+0);
my $d = (2 * $delta_min) - $delta_maj;
my $d_inc1 = $delta_min * 2;
my $d_inc2 = ($delta_min - $delta_maj) * 2;
my @points;
{
my @point =
$dir ?
($curr_maj, $curr_min)
: ($curr_min, $curr_maj);
push @points,
defined $callback ?
$callback->(@point)
: [@point];
last if $curr_maj == $to_maj;
$curr_maj += $inc_maj;
if ($d < 0) {
$d += $d_inc1;
} else {
$d += $d_inc2;
$curr_min += $inc_min;
}
redo;
}
return @points;
}
sub circle {
my ($y, $x, $radius) = @_;
my ($curr_x, $curr_y) = (0, $radius);
my $d = 3 - (2 * $radius);
my @points;
{
push @points, [$y + $curr_y, $x + $curr_x];
push @points, [$y + $curr_y, $x - $curr_x];
push @points, [$y - $curr_y, $x + $curr_x];
push @points, [$y - $curr_y, $x - $curr_x];
push @points, [$y + $curr_x, $x + $curr_y];
push @points, [$y + $curr_x, $x - $curr_y];
push @points, [$y - $curr_x, $x + $curr_y];
push @points, [$y - $curr_x, $x - $curr_y];
last if $curr_x >= $curr_y;
if ($d < 0) {
$d += (4 * $curr_x) + 6;
} else {
$d += 4 * ($curr_x - $curr_y) + 10;
$curr_y -= 1;
}
$curr_x++;
redo;
}
return @points;
}
sub sig {
# returns: +1, 0, -1 depending on sign
$_[0] or return 0;
return abs($_[0]) == $_[0] ? 1 : -1;
}
###
1;
__END__