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

      } #/* now horizontal cut at P4 comes first */
     }
    $t = ($x0-$x1)/$t;
    $r = (1-$t)*((1-$t)*$y0+2.0*$t*$y1)+$t*$t*$y2;# /* By(t=P4) */
    $t = ($x0*$x2-$x1*$x1)*$t/($x0-$x1); #/* gradient dP4/dx=0 */
    $x = int($t+0.5); $y = int($r+0.5);
    $r = ($y1-$y0)*($t-$x0)/($x1-$x0)+$y0; #/* intersect P3 | P0 P1 */
    push @points, basic_bezier($x0,$y0, $x,int($r+0.5), $x,$y);
    $r = ($y1-$y2)*($t-$x2)/($x1-$x2)+$y2; #/* intersect P4 | P1 P2 */
    $x0 = $x1 = $x; $y0 = $y; $y1 = int($r+0.5);# /* P0 = P4, P1 = P8 */
  }
  if (($y0-$y1)*($y2-$y1) > 0) { #/* vertical cut at P6? */
    $t = $y0-2*$y1+$y2; $t = ($y0-$y1)/$t;
    $r = (1-$t)*((1-$t)*$x0+2.0*$t*$x1)+$t*$t*$x2; # /* Bx(t=P6) */
    $t = ($y0*$y2-$y1*$y1)*$t/($y0-$y1); #/* gradient dP6/dy=0 */
    $x = int($r+0.5); $y = int($t+0.5);
    $r = ($x1-$x0)*($t-$y0)/($y1-$y0)+$x0; #/* intersect P6 | P0 P1 */
     push @points, basic_bezier($x0,$y0, int($r+0.5),$y, $x,$y);
    $r = ($x1-$x2)*($t-$y2)/($y1-$y2)+$x2; #/* intersect P7 | P1 P2 */
    $x0 = $x; $x1 = int($r+0.5); $y0 = $y1 = $y;# /* P0 = P6, P1 = P7 */
  }
   push @points, basic_bezier($x0,$y0, $x1,$y1, $x2,$y2); #/* remaining part */
   return @points;
}

=head2 C<polyline>

    my @points = polyline ($x0, $y0, $x1, $y1, $x2, $y2)

Draws a polyline between points served as a list of x,y pairs

=cut

sub polyline{
	my @vertices;
	push @vertices,[shift,shift] while (@_>1);
	my @points;
	foreach my $vertex(0..(@vertices-2)){
		push @points,line(@{$vertices[$vertex]},@{$vertices[$vertex+1]});	
		pop @points if ($vertex < (@vertices-2)); # remove duplicated points
	}
	return @points;
}

=head2 C<thick_line>

    my @points = thick_line ($x0, $y0, $x1, $y1,$thickness)

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;
  my $E_square= 2*$dy;
  my $p=my $q=0;

  my $y= $y0;
  my $x= $x0;
  my $error= $einit;
  my $tk= $dx+$dy-$winit; 

  while($tk<=$w_left)
  {
     push (@pts,[$x,$y]);
     if ($error>=$threshold)
     {
       $x= $x + $xstep;
       $error = $error + $E_diag;
       $tk= $tk + 2*$dy;
     }
     $error = $error + $E_square;
     $y= $y + $ystep;
     $tk= $tk + 2*$dx;
     $q++;
  }

  $y= $y0;
  $x= $x0;
  $error= -$einit;
  $tk= $dx+$dy+$winit;

  while($tk<=$w_right)
  {
     push (@pts,[$x,$y]) if ($p);
     if ($error>$threshold)
     {
       $x= $x - $xstep;
       $error = $error + $E_diag;
       $tk= $tk + 2*$dy;
     }