outfile:write(json.encode({mode=shape.mode, center=drawing.points[shape.center], radius=shape.radius, start_angle=shape.start_angle, end_angle=shape.end_angle}))
      outfile:write('\n')
    elseif shape.mode == 'deleted' then
      -- ignore
    else
      print(shape.mode)
      assert(false)
    end
  end
  outfile:write('```\n')
      outfile:write(json.encode({mode=shape.mode, center=drawing.points[shape.center], radius=shape.radius}))
      outfile:write('\n')
    elseif shape.mode == 'arc' then
      outfile:write(line)
      outfile:write('\n')
    elseif shape.mode == 'circle' then
      outfile:write(line)
      outfile:write('\n')
    elseif shape.mode == 'polygon' or shape.mode == 'rectangle' or shape.mode == 'square' then
      local obj = {mode=shape.mode, vertices={}}
      for _,p in ipairs(shape.vertices) do
        table.insert(obj.vertices, drawing.points[p])
      end
      local line = json.encode(obj)
      outfile:write(json.encode(shape))
      outfile:write('\n')
    elseif shape.mode == 'line' or shape.mode == 'manhattan' then
      local line = json.encode({mode=shape.mode, p1=drawing.points[shape.p1], p2=drawing.points[shape.p2]})