function r = browniantree(xsize, ysize = xsize, numparticle = 1000)
  r = zeros(xsize, ysize, "uint8");
  r(unidrnd(xsize), unidrnd(ysize)) = 1;

  for i = 1:numparticle
    px = unidrnd(xsize-1)+1;
    py = unidrnd(ysize-1)+1;
    while(1)
      dx = unidrnd(2) - 1;
      dy = unidrnd(2) - 1;
      if ( (dx+px < 1) || (dx+px > xsize) || (dy+py < 1) || (dy+py > ysize) )
	px = unidrnd(xsize-1)+1;
	py = unidrnd(ysize-1)+1;
      elseif ( r(px+dx, py+dy) != 0 )
	r(px, py) = 1;
	break;
      else
	px += dx;
	py += dy;
      endif
    endwhile
  endfor
endfunction

r = browniantree(200);
r( r > 0 ) = 255;
jpgwrite("browniantree.jpg", r, 100); % image package