Tricia Francis on "How to add classes to images based on their categories?"

I need to be able to: 1.) assign categories to images and 2.) add classes to all images that correspond to their assigned categories.

I was able to add categories to images with the following:

function ug_add_categories_to_attachments() {
    register_taxonomy_for_object_type( 'category', 'attachment' );
}
add_action( 'init' , 'ug_add_categories_to_attachments' );

And I found a function to add a class to images as so:

function add_image_class($class){
	$class .= ' additional-class';
	return $class;
}
add_filter('get_image_tag_class','add_image_class');

But I'm not advanced enough with php to take it much further. I tried this

function ug_add_image_class($class){
	foreach(get_the_category() as $cat) { $class .= ' category-'.$cat->slug; };
	return $class;
}
add_filter('get_image_tag_class','ug_add_image_class');

but no love...

Help? Ideas? Please? and Happy Friday!