Easy Image Gallery - Change the thumbnail size depending on the post type

gistfile1.php

<?php
/**
 * Change the thumbnail size depending on the post type
*/
function sumobi_eig_thumbnail_image_size( $image_size ) {
	$post_type = get_post_type();

	switch ( $post_type ) {
		// post's will use the 'medium' size from Settings -> Media
		case 'post':
			$image_size = 'medium';
			break;

		// pages's will use the a custom image size added with add_image_size
		case 'page':
			$image_size = 'custom-image-size';
			break;	
		
		// all other post types will use the standard 'thumbnail' size from Settings -> Media
		default:
			$image_size = 'thumbnail';
			break;
	}

	return $image_size;
}
add_filter( 'easy_image_gallery_thumbnail_image_size', 'sumobi_eig_thumbnail_image_size' );