基於Bresenahams的畫直線演算法(J2ME版)

大名鼎鼎的Bresenahams畫線演算法,現在改成了J2ME版,此演算法沒有任何乘除運算,只有加減運算,效率很高.

/**
  * @todo 基於Bresenahams的畫直線演算法
  * @param g Graphics類
  * @param x0 起點的x座標
  * @param y0 起點的y座標
  * @param x1 終點的x座標
  * @param y1 終點的y座標
    **/
 private void drawLine2(Graphics g,int x0,int y0,int x1,int y1)
 {
  int dx,dy,dx2,dy2,x_inc,y_inc,e,index;
  dx = x1 - x0; //deltas x
  dy = y1 - y0; //deltas y
  if(dx >= 0)
  {
   x_inc = 1;
  }
  else
  {
   x_inc = -1;
   dx = -dx;
  }
  if(dy >= 0)
  {
   y_inc = 1;
  }
  else
  {
   y_inc = -1;
   dy = -dy;
  }
  dx2 = dx << 1; //dx*2
  dy2 = dy << 1; //dy*2
  if(dx > dy)
  {
   e = dy2 - dx;
   for(index = 0;index <= dx;index++)
   {
    //draw point
    g.drawLine(x0,y0,x0,y0);
    //compute next point
    if (e >= 0)
          {
            e-=dx2;
            y0+=y_inc;
       }
    e+=dy2;
       x0+=x_inc;
   }
  }
  else
  {
     e = dx2 - dy;
     for (index=0; index <= dy; index++)
     {
      //draw point
      g.drawLine(x0,y0,x0,y0);
      //compute next point
         if (e >= 0)
         {
            e-=dy2;
            x0+=x_inc;
         }
         e+=dx2;
         y0+=y_inc;
     }
  }
 }