You can use the image resizer object functions outside of the UI with a small amount of hand code like:
<?php require_once( "webassist/caching/CachedResize_Image.php" ); ?>
<?php
$image = new CachedResize_Image;
$newSrc = $image->get_from_cache(30,30,"images/logo.jpg","images/cache", "crop", "", "", "");
echo($newSrc);
?>