Complete example of PHP encapsulated picture (thumbnail) processing class

<?php
//图片处理工具类
class Image{
    //属性
    private $thumb_width; //缩略图的宽
    private $thumb_height;
    //错误属性
    public $thumb_error;
    //构造方法
    public function __construct($width = 0,$height = 0){
      $this->thumb_width = ($width == 0) ? $GLOBALS[&#39;config&#39;][&#39;admin_goods_thumb&#39;][&#39;width&#39;] : $width;
      $this->thumb_height = ($height == 0) ? $GLOBALS[&#39;config&#39;][&#39;admin_goods_thumb&#39;][&#39;height&#39;] : $height;
    }
    /*
     * 制作缩略图
     * @param1 string $src，原图路径，/uploads/20150122101010abcdef.gif
     * @param2 string $path，缩略图保存路径/uploads/thumb_20150122101010abcdef.gif
     * @return 缩略图的名字
    */
    public function makeThumb($src,$path){
      //判断原图是否存在
      if(!file_exists($src)){
        $this->thumb_error = &#39;原图不存在！&#39;;
        return false;
      }
      //打开原图资源
      //获取能够使用的后缀
      $ext = $this->getFunctionName($src); //gif
      //拼凑函数名
      $open = &#39;imagecreatefrom&#39; . $ext;    //imagecreatefromgif
      $save = &#39;image&#39; . $ext;          //imagegif
      //如果不清楚；echo $open,$save;exit;
      //可变函数打开原图资源
      $src_img = $open($src); //利用可变函数打开图片资源
      //imagecreatefromgif($src)
      //缩略图资源
      $dst_img = imagecreatetruecolor($this->thumb_width,$this->thumb_height);
      //背景色填充白色
      $dst_bg_color = imagecolorallocate($dst_img,255,255,255);
      imagefill($dst_img,0,0,$dst_bg_color);
      //宽高比确定宽高
      $dst_size = $this->thumb_width / $this->thumb_height;
      //获取原图数据
      $file_info = getimagesize($src);
      $src_size = $file_info[0]/$file_info[1];
      //求出缩略图宽和高
      if($src_size > $dst_size){
        //原图宽高比大于缩略图
        $width = $this->thumb_width;
        $height = round($width / $src_size);
      }else{
        $height = $this->thumb_height;
        $width = round($height * $src_size);
      }
      //求出缩略图起始位置
      $dst_x = round($this->thumb_width - $width)/2;
      $dst_y = round($this->thumb_height - $height)/2;
      //制作缩略图
      if(imagecopyresampled($dst_img,$src_img,$dst_x,$dst_y,0,0,$width,$height,$file_info[0],$file_info[1])){
        //采样成功：保存，将文件保存到对应的路径下
        $thumb_name = &#39;thumb_&#39; . basename($src);
        $save($dst_img,$path . &#39;/&#39; . $thumb_name);
        //保存成功
        return $thumb_name;
      }else{
        //采样失败
        $this->thumb_error = &#39;缩略图采样失败！&#39;;
        return false;
      }
    }
    /*
     * 获取文件要调用的函数名
     * @param1 string $file，文件名字
     * @return 通过文件后缀名得到的函数字符串
    */
    private function getFunctionName($file){
      //得到文件的后缀
      $file_info = pathinfo($file);
      $ext = $file_info[&#39;extension&#39;]; //后缀：gif,png,jpg,jpeg,pjpeg
      //imagecreatefromgif,imagecreatefromjpeg,imagecreatefrompng
      //定义一个数组保存函数名
      $func = array(
        &#39;gif&#39; => &#39;gif&#39;,
        &#39;png&#39; => &#39;png&#39;,
        &#39;jpg&#39; => &#39;jpeg&#39;,
        &#39;jpeg&#39; => &#39;jpeg&#39;,
        &#39;pjpeg&#39; => &#39;jpeg&#39;
      );
      //返回值
      return $func[$ext];
    }
}