This hook is used to alter the resize of gif images. By default OSSN changes gif to non animated gifs.

<?php
function my_component_init(){
		ossn_add_hook('ossn', 'image:resize:gif', 'my_component_hook');
}
function my_component_hook($hook, $type, $return, $params){
		//$params[max_width], $params[max_height] , $params[file_path]
		//if resized 
		//return image as a string;
}
ossn_register_callback('ossn', 'init', 'my_component_init');

Example of this use case https://www.opensource-socialnetwork.org/component/view/3456/animated-gif-support