Image helper test script

<?php

include 'app/Mage.php'; // adjust as required

Mage::app()->setCurrentStore(1); // use whatever one of your store ID/codes is

$product = Mage::getModel('catalog/product')->loadByAttribute('sku', 'YOURSKU'); // put your product sku in

var_dump((string) Mage::helper('catalog/image')->init($product, 'thumbnail')->resize(50, 50));