Category image resize in Magento

<?php
$_file_name = $cat->getThumbnail();             
$_media_dir = Mage::getBaseDir('media') . DS . 'catalog' . DS . 'category' . DS;
$cache_dir = $_media_dir . 'resize' . DS;

if (file_exists($cache_dir . $_file_name)) {
$catImg =Mage::getBaseUrl('media') .  'catalog' . DS . 'category' . DS . 'resize' . DS . $_file_name;
 } elseif (file_exists($_media_dir . $_file_name)) {
if (!is_dir($cache_dir)) {
mkdir($cache_dir);
}

$_image = new Varien_Image($_media_dir . $_file_name);
$_image->constrainOnly(true);
$_image->keepAspectRatio(false);
$_image->keepFrame(false);
$_image->keepTransparency(true);
$_image->resize(224, 174); // change image height, width
$_image->save($cache_dir . $_file_name);
$catImg = Mage::getBaseUrl('media') . 'catalog' . DS . 'category' . DS . 'resize' . DS . $_file_name;
                         }
 echo  $catImg ; // display resize category thumbnail imagename
 ?>

<img src="<?php echo $catImg;  ?>"  />