用PHP写一个完美GIF图片等比缩放类,附带去除缩放黑背景

<?php
class resize_image{
   private $o_img_width;//原图像宽度
   private $o_img_height;//原图像高度
   private $n_img_width;//新图像宽度
   private $n_img_height;//新图像高度
   private $o_img_file;//原图像文件
   private $o_img_source;//原图像资源
   private $n_img_file;//新图像资源
   private $n_img_source;//新图像资源
   private $o_to_n_per=0.5;//图像缩放比

   //初始化内部变量
   function __construct($oldfile,$newfile){
       list($width,$height)=getimagesize($oldfile);
       $this->o_img_file=$oldfile;
       $this->o_img_width=$width;
       $this->o_img_height=$height;
       $this->n_img_file=$newfile;
   }

   //等比例缩放并且解决GIF透明色为黑色背景的问题
   function get_resize_scaling_img(){
       $this->n_img_width=$this->o_img_width*$this->o_to_n_per;
       $this->n_img_height=$this->o_img_height*$this->o_to_n_per;
       //等比例缩放图片(算法)
       if ( $this->n_img_width && ( $this->o_img_width <$this->o_img_height))
       {
             $this->n_img_width = ( $this->n_img_height/$this->o_img_height) * $this->o_img_width;
       }
       else
       {
            $this->n_img_height = ($this->n_img_width / $this->o_img_width) * $this->o_img_height;
       }
       $this->o_img_source=imagecreatefromgif($this->o_img_file);
       //创建一个等比例缩放大小的画布
       $this->n_img_source=imagecreatetruecolor($this->o_img_width,$this->n_img_height);

       //美化:去除黑色不透明背景
       $trans_init=imagecolortransparent($this->o_img_source);
       //寻找透明色并且判断是否在总颜色中
       if($trans_init>=0 && $trans_init < imagecolorstotal($this->o_img_source)){
           //如果在的话则搜索这个颜色的RGB色相
           $trans_index=imagecolorsforindex($this->o_img_source,$trans_init);
           //找到之后就创建这样一个颜色
           $trans_new=imagecolorallocate($this->n_img_source,$trans_index["red"],$trans_index["green"],$trans_index["blue"]);
           //然后我们用这个颜色去填充新的图像
           imagefill($this->n_img_source,0,0,$trans_new);
           //然后我们在把填充色设置为透明
           imagecolortransparent($this->n_img_source,$trans_new);
       }
       //拷贝原图像到新画板上
       imagecopyresized($this->n_img_source,$this->o_img_source,0,0,0,0,$this->n_img_width,$this->n_img_height,$this->o_img_width,$this->o_img_height);
       return $this->n_img_source;
   }
   //最终销毁资源
   function __destruct(){
       imagedestroy($this->o_img_source);
       imagedestroy($this->n_img_source);
       
   }

}