object BitmapOps {
   def bresenham(bm:RgbBitmap, x0:Int, y0:Int, x1:Int, y1:Int, c:Color)={
      val dx=math.abs(x1-x0)
      val sx=if (x0<x1) 1 else -1
      val dy=math.abs(y1-y0)
      val sy=if (y0<y1) 1 else -1

      def it=new Iterator[Tuple2[Int,Int]]{
         var x=x0; var y=y0
         var err=(if (dx>dy) dx else -dy)/2
         def next={
            val res=(x,y)
            val e2=err;
            if (e2 > -dx) {err-=dy; x+=sx}
            if (e2<dy) {err+=dx; y+=sy}
            res;
         }
         def hasNext = (sx*x <= sx*x1 && sy*y <= sy*y1)
      }

      for((x,y) <- it)
         bm.setPixel(x, y, c)
   }
}