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lib/Algorithm/Line/Bresenham.pm  view on Meta::CPAN

Draws a line thickened using Murphy's modication of Bresenham'salgorithm
between two points  of x,y pairs. This routine was further enahnced to 
provide variable thickness lines and uses multiple helper subroutines.

=head2 C<varthick_line>
  
  my @points= varthick_line($x0,$y0,$x1,$y1,$leftFn,$argL,$rightFn,$argR)

Variable thickness lines are implemented as described in
http://kt8216.unixcab.org/murphy/index.html ; This allows passing of 
two subroutine references (so the left side and the right sides of the
line can have differently varying thicknesses) along with a
user originated parameter. The subroutine reference example is shown below:

   my $leftFn=sub{
      my ($arg,$p,$l)=@_;
      # C<$arg> is passed by calling routine,
      # C<$p> is point on line
      # C<$l> is length of line
	  return $p % $arg;
   };

=cut

## Variable thickness lines using Murphy's Modification of Bresenham Line Algorithm**
## Codes ported from C in http://kt8216.unixcab.org/murphy/index.html  

 #*                            X BASED LINES                            *
 
sub x_perpendicular{
  my ($x0,$y0,$dx,$dy,$xstep,$ystep,$einit,$w_left,$w_right,$winit)=@_;
  
  my @pts;

  my $threshold = $dx - 2*$dy;
  my $E_diag= -2*$dx;