What is this filtering algorithm called?

Hello, can somebody explain to me how the following code works or tell me the name of the method used to filter the left binary image to the right one?

Image:

Code:

[rows, cols] = size(e);

L1 = 20;
L2 = 80;
seed = [];

for alpha = 40:120
    dx = cos( alpha * pi / 180);
    dy = sin( alpha * pi / 180);

      for d = L1:L2
          r =  round(cy - d * dy );
          c =  round(cx + d * dx );

          found = 0;

          for i = -2:2
              for j=-2:2
                  ri = r + i;
                  cj = c + j;

                  if( ri < 1 || ri > rows || cj < 1 || cj > cols || found )
                      continue;
                  end;

                  if( e(ri, cj) )
                      found = 1;
                      seed = [ seed, sub2ind( [rows, cols], ri, cj ) ];
                  end;
              end;
          end;

          if( found>0 )
              break;
          end;
      end;
  end;

newe = ones( rows, cols ) > 2;

for k=1:length(seed)
    [r,c] = ind2sub( [rows, cols], seed(k) );

      if( e(r,c)  )
          e(r,c) = 0;
          q = seed(k);
          newe(r,c) = 1;

          while( ~isempty(q) )
              id = q(1); q = q(2:end);
              [r,c] = ind2sub( [rows, cols],id);

              for i=-1:1
                  for j=-1:1
                      ri = r+i;
                      cj = c+j;

                      if( ri < 1 || ri > rows || cj < 1 || cj > cols )
                          continue;
                      end;

                      if( e(ri, cj)  )
                          e(ri, cj) = 0;
                          newe( ri, cj ) = 1;
                          q = [q, sub2ind( [rows, cols], ri, cj ) ];
                      end;
                  end;
              end;
          end;
      end;
  end;

newe = bwmorph( newe, 'dilate', 2 ); 
newe = bwmorph( newe, 'thin', inf );