PHP实现图片缩放功能支持多种格式

function getSizeImage($filename,$new_width,$new_height){
 
list($width, $height)=getimagesize($filename);
 
$n_w=$width/$new_width;
 
$n_h=$height/$new_height;
 
$n_w = $width/$n_w;
 
$n_h = $height/$n_h;
 
$new=imagecreatetruecolor($n_w, $n_h);+
 
$ext = (@end(explode(".",$filename)));
 
switch ($ext) {
 
    case 'png':
       $img = imagecreatefrompng($filename);
    break;
 
    case 'gif':
      $img = imagecreatefromgif($filename);
    break;
 
    case 'jpeg':
      $img = imagecreatefromjpeg($filename);
    break;
 
    case 'jpg':
     $img = imagecreatefromjpeg($filename);
    break;
 
    default:
      dd('不支持该类型');
    break;
 
}
 
 
//copy部分图像并调整
 
imagecopyresized($new, $img,0, 0,0, 0,$n_w, $n_h, $width, $height);
 
//图像输出新图片、另存为
 
imagejpeg($new,$filename);
 
imagedestroy($new);
 
imagedestroy($img);
 
}