How to create a category and add an image programatically - magento-1.7

Question

I've written a script that creates a category and adds a thumbnail image. It is inserted in the database but the thumbnail is not displayed.
When I upload from the backend it works fine.
This is my code.
<?php
require_once 'businessclasses.php';
define('MAGENTO', realpath(dirname(__FILE__)));
require_once MAGENTO . '/app/Mage.php';
umask(0);
Mage::app()->setCurrentStore(1); // Mage_Core_Model_App::ADMIN_STORE_ID
$count = 0;
importRootCategories('us', '1/31/32', 4);
function importRootCategories($language, $path, $storeID)
{
$data = new getCSV();
$rows = $data->getRootCategories(); // Gets the list of root categories.
foreach($rows as $row) {
$categoryName = utf8_decode(iconv('ISO-8859-1','UTF-8',strip_tags(trim($row[$language])))); // Name of Category
if($language == "us") {
if($row[$language] == "")
$categoryName = utf8_decode(iconv('ISO-8859-1','UTF-8',strip_tags(trim($row["en"])))); // Name of Category
}
// Create category object
$category = Mage::getModel('catalog/category');
$category->setStoreId($storeID); // 'US-Store' store is assigned to this category
$rootCategory['name'] = $categoryName;
$rootCategory['path'] = $path; // this is the catgeory path - 1 for root category
$rootCategory['display_mode'] = "PRODUCTS";
$rootCategory['include_in_menu'] = 1;
$rootCategory['is_active'] = 1;
$rootCategory['is_anchor'] = 1;
$rootCategory['thumbnail'] = _getCategoryImageFile($row['catimg'].'.jpg');
$category->addData($rootCategory);
try {
$category->save();
echo $rootCategoryId = $category->getId();
}
catch (Exception $e){
echo $e->getMessage();
}
}
}
function _getCategoryImageFile($filename)
{
$filePath = Mage::getBaseDir('media') . DS . 'catalog' . DS . 'category' . DS . $filename;
$fileUrl = Mage::getBaseUrl(Mage_Core_Model_Store::URL_TYPE_MEDIA) . 'import/category/'. $filename;
$imageUrl=file_get_contents($imageUrl);
$file_handler=fopen($filePath,'w');
if(fwrite($file_handler,$fileUrl)==false){
Mage::log('ERROR: ', null,'error');
}
else{
Mage::log('Image Created Successfully', null, '');
}
fclose($file_handler);
return $filename;
}
?>