怎么使用php的gd库画一条抗锯齿的粗斜线

create(func_get_arc(0),func_get_arc(1));
    else
        $this->create(400,300);
  }
  /**
   * 在($x,$y)处画点
   */
  function pixel($x,$y) {
    $p = $this->get_view($x,$y);
    imagesetpixel($this->im,$p['x'],$p['y'],$this->color);
    $this->xo = $p['x'];
    $this->yo = $p['y'];
  }
  /**
   * 移动到($x,$y)处
   */
  function moveto($x,$y) {
    $p = $this->get_view($x,$y);
    $this->xo = $p['x'];
    $this->yo = $p['y'];
  }
  /**
   * 从($x1,$y1)到($x2,$y2)处画线
   */
  function line($x1,$y1,$x2,$y2) {
    $p1 = $this->get_view($x1,$y1);
    $p2 = $this->get_view($x2,$y2);
    imageline($this->im,$p1['x'],$p1['y'],$p2['x'],$p2['y'],$this->color);
  }
  /**
   * 从当前位置到($x,$y)处画线
   */
  function lineto($x,$y) {
    $p = $this->get_view($x,$y);
    imageline($this->im, $this->xo, $this->yo, $p['x'], $p['y'], $this->color);
    $this->xo = $p['x'];
    $this->yo = $p['y'];
  }
  /**
   * 设置当前颜色
   */
  function color($clr) {
    $r = ($clr>>16) & 0xff; 
    $g = ($clr>>8) & 0xff; 
    $b = ($clr) & 0xff; 
    $this->color = ImageColorAllocate($this->im, $r,$g,$b);
    $this->fillcolor = ImageColorAllocate($this->im, $r,$g,$b);
    $this->filldarkcolor = ImageColorAllocate($this->im, $r/2,$g/2,$b/2);
    return $this->color;
  }
  /**
   * 设置当前充填颜色
   */
  function fillcolor($clr) {
    $r = ($clr>>16) & 0xff; 
    $g = ($clr>>8) & 0xff; 
    $b = ($clr) & 0xff; 
    $this->fillcolor = ImageColorAllocate($this->im, $r,$g,$b);
    return $this->fillcolor;
  }
  /**
   * 创建GD句柄并设置坐标系
   */
  function create($x,$y) {
    $this->im = imagecreatetruecolor($x,$y);
imageantialias($this->im, 1);
imagefill($this->im, 0, 0, $this->color(0xffffff));
    $this->viewx = $x-1;
    $this->viewy = -($y-1);
    $this->winx = $x;
    $this->winy = $y;
    $this->orgx = 0;
    $this->orgy = 0;//$y;
    $this->colors = $this->color(0xffffff);

    settype($this->ksin,"double");
    settype($this->kcos,"double");
    $this->ksin = sin(deg2rad(0));
    $this->kcos = cos(deg2rad(0));
  }
  /**
   * 坐标映射
   */
  function get_view($x,$y) {
    $this->xo = $x*$this->kcos - $y*$this->ksin;
    $this->yo = $x*$this->ksin + $y*$this->kcos;
    $p['x'] = ($this->xo + $this->orgx)*($this->viewx/$this->winx);
    $p['y'] = ($this->yo + $this->orgy)*($this->viewy/$this->winy)-$this->viewy;
    return $p;
  }
  /**
   * 设置限度
   */
  function set_ext($x,$y=0) {
    $this->winx = $x;
    if($y == 0) {
        $this->winy = - $x * $this->viewy / $this->viewx;
    }else {
        $this->winy = $y;
    }
  }
  /**
   * 设置旋转角
   */
  function set_r($p) {
    $this->ksin = sin(deg2rad($p));
    $this->kcos = cos(deg2rad($p));
  }
  /**
   * 构造图形，必需在派生类中重载本方法
   */
  function paint() {
    /**
     * 必需由派生类重载
     * 必需包含语句 $this->create(宽度,高度);
     */
    die("paint 方法必需由派生类重载!");
  }
  /**
   *