PHP处理图片成指定大小的缩略图--简单封装的类

<?PHP
//图像处理类
class Image {
    private $file;    //图片地址
    private $width;   //图片长度
    private $height;   //图片长度
    private $type;    //图片类型
    private $img;    //原图的资源句柄
    private $new;    //新图的资源句柄
 
    //构造方法，初始化
    public function __construct($_file) {
        $this->file = $_file;
        list($this->width, $this->height, $this->type) = getimagesize($this->file);
        $this->img = $this->getFromImg($this->file, $this->type);
    }
    //缩略图(固定长高容器，图像等比例，扩容填充，裁剪)[固定了大小，不失真，不变形]
    public function thumb($new_width = 0,$new_height = 0) {
  
        if (empty($new_width) && empty($new_height)) {
			$new_width = $this->width;
			$new_height = $this->height;
        }
  
		if (!is_numeric($new_width) || !is_numeric($new_height)) {
			$new_width = $this->width;
			$new_height = $this->height;
		}
  
		//创建一个容器
		$_n_w = $new_width;
		$_n_h = $new_height;
	  
		//创建裁剪点
		$_cut_width = 0;
		$_cut_height = 0;
	  
		if ($this->width < $this->height) {
			$new_width = ($new_height / $this->height) * $this->width;
		} else {
			$new_height = ($new_width / $this->width) * $this->height;
		}
		if ($new_width < $_n_w) { //如果新高度小于新容器高度
			$r = $_n_w / $new_width; //按长度求出等比例因子
			$new_width *= $r; //扩展填充后的长度
			$new_height *= $r; //扩展填充后的高度
			$_cut_height = ($new_height - $_n_h) / 2; //求出裁剪点的高度
		}
	  
		if ($new_height < $_n_h) { //如果新高度小于容器高度
			$r = $_n_h / $new_height; //按高度求出等比例因子
			$new_width *= $r; //扩展填充后的长度
			$new_height *= $r; //扩展填充后的高度
			$_cut_width = ($new_width - $_n_w) / 2; //求出裁剪点的长度
		}
 
        $this->new = imagecreatetruecolor($_n_w,$_n_h);
        imagecopyresampled($this->new,$this->img,0,0,$_cut_width,$_cut_height,$new_width,$new_height,$this->width,$this->height);
    }
 
    //加载图片，各种类型，返回图片的资源句柄
    private function getFromImg($_file, $_type) {
        switch ($_type) {
			case 1 :
				$img = imagecreatefromgif($_file);
				break;
			case 2 :
				$img = imagecreatefromjpeg($_file);
				break;
			case 3 : 
				$img = imagecreatefrompng($_file);
				break;
			default:
				$img = '';
        }
        return $img;
    }
 
    //图像输出
    public function out() {
        imagepng($this->new,$this->file);//第二个参数为新生成的图片名
        imagedestroy($this->img);
        imagedestroy($this->new);
    }
}
//使用demo
$_path = '1.jpg';//$_path为图片文件的路径
$_img = new Image($_path);
$_img->thumb(100, 100);
$_img->out();
?>