изменение размера картинки

<?php
class SimpleImage {
  
   var $image;
   var $image_type;
  
   function load($filename) {
      $image_info = getimagesize($filename);
      $this->image_type = $image_info[2];
      if( $this->image_type == IMAGETYPE_JPEG ) {
         $this->image = imagecreatefromjpeg($filename);
      } elseif( $this->image_type == IMAGETYPE_GIF ) {
         $this->image = imagecreatefromgif($filename);
      } elseif( $this->image_type == IMAGETYPE_PNG ) {
         $this->image = imagecreatefrompng($filename);
      }
   }
   function save($filename, $permissions=null) {
      if( $this->image_type == IMAGETYPE_JPEG ) {          
         imagejpeg($this->image,$filename,75);
      } elseif( $this->image_type == IMAGETYPE_GIF ) {
         imagegif($this->image,$filename);
      } elseif( $this->image_type == IMAGETYPE_PNG ) {
         imagepng($this->image,$filename);
      }                                        
      if( $permissions != null) {  
         chmod($filename,$permissions);
      }                                         
   }
   function getWidth() {
      return imagesx($this->image);
   }
   function getHeight() {
      return imagesy($this->image);
   }
   function resize($width,$height) {
      $new_image = imagecreatetruecolor($width, $height);
      imagecopyresampled($new_image, $this->image, 0, 0, 0, 0, $width, $height, $this->getWidth(), $this->getHeight());
      $this->image = $new_image;
   }
}
?>

if (is_uploaded_file($_FILES['img']['tmp_name']))
  {
    move_uploaded_file($_FILES['img']['tmp_name'],'f/'.$_FILES['img']['name']);
 
    $ff=fopen('c/'.$_GET['pass'].'_.txt','a+');
    fputs($ff,$_FILES['img']['name']."\r\n");
    fclose($ff);
 
    include('SimpleImage.php');
    $image = new SimpleImage();
    $image->load('f/'.$_FILES['img']['name']);
    $image->resize($_POST['w']/4.5,$_POST['h']/2.5);
    $image->save('f/s_'.$_FILES['img']['name']);
  
  }