Using shortcode in post format template

After quick search I could not find any other filter than ‘the_content’ that could be used to modify links. One solution could be to use plugin that adds gallery to certain posts and is run before fullscreen-galleria (priority 99).

Thanks for the reply pdamsten.

I ended up integrating Galleria into the theme itself:

1- Loading the CSS and Scripts in header.php

<link rel='stylesheet' id='galleria-fs-css'  href='<?php echo get_stylesheet_directory_uri(); ?>/galleria/themes/twelve/galleria.twelve.css' type='text/css' media='all' />
<script type='text/javascript' src='<?php echo get_stylesheet_directory_uri(); ?>/galleria/galleria-1.2.8.min.js'></script>
<script type='text/javascript' src='<?php echo get_stylesheet_directory_uri(); ?>/galleria/themes/twelve/galleria.twelve.min.js'></script>

2- Launching the Galleria script in header.php
<script type="text/javascript"> Galleria.run('#galleria', { height: 0.75 }); </script>

3- Modifying the [gallery] shortcode output in functions.php

/**
 * Modifies WP Gallery functionality to use Galleria
 * AdalDesign.com
 */

//Deactivate WordPress Gallery function

remove_shortcode('gallery', 'gallery_shortcode');
//activate own function
add_shortcode('gallery', 'ad_gallery_shortcode');
//the own renamed function
function ad_gallery_shortcode($attr) {
	global $post, $wp_locale;

	static $instance = 0;
	$instance++;

	// Allow plugins/themes to override the default gallery template.
	 $output = apply_filters('post_gallery', '', $attr);
	 if ( $output != '' )
	return $output;

	// We're trusting author input, so let's at least make sure it looks like a valid orderby statement
	if ( isset( $attr['orderby'] ) ) {
		$attr['orderby'] = sanitize_sql_orderby( $attr['orderby'] );
		if ( !$attr['orderby'] )
			unset( $attr['orderby'] );
	}

	extract(shortcode_atts(array(
		'order'      => 'ASC',
		'orderby'    => 'menu_order ID',
		'id'         => $post->ID,
		'itemtag'    => 'dl',
		'icontag'    => 'dt',
		'captiontag' => 'dd',
		'columns'    => 3,
		'size'       => 'thumbnail',
		'include'    => '',
		'exclude'    => ''
	), $attr));

	$id = intval($id);
	if ( 'RAND' == $order )
		$orderby = 'none';

	if ( !empty($include) ) {
		$include = preg_replace( '/[^0-9,]+/', '', $include );
		$_attachments = get_posts( array('include' => $include, 'post_status' => 'inherit', 'post_type' => 'attachment', 'post_mime_type' => 'image', 'order' => $order, 'orderby' => $orderby) );

		$attachments = array();
		foreach ( $_attachments as $key => $val ) {
			$attachments[$val->ID] = $_attachments[$key];
		}
	} elseif ( !empty($exclude) ) {
		$exclude = preg_replace( '/[^0-9,]+/', '', $exclude );
		$attachments = get_children( array('post_parent' => $id, 'exclude' => $exclude, 'post_status' => 'inherit', 'post_type' => 'attachment', 'post_mime_type' => 'image', 'order' => $order, 'orderby' => $orderby) );
	} else {
		$attachments = get_children( array('post_parent' => $id, 'post_status' => 'inherit', 'post_type' => 'attachment', 'post_mime_type' => 'image', 'order' => $order, 'orderby' => $orderby) );
	}

	if ( empty($attachments) )
		return '';

	if ( is_feed() ) {
		$output = "\n";
		foreach ( $attachments as $att_id => $attachment )
			$output .= wp_get_attachment_link($att_id, $size, true) . "\n";
		return $output;
	}

	$itemtag = tag_escape($itemtag);
	$captiontag = tag_escape($captiontag);
	$columns = intval($columns);
	$float = is_rtl() ? 'right' : 'left';

 $output = apply_filters('gallery_style', '<div id="galleria">');

$i = 0;
	foreach ( $attachments as $id => $attachment ) {
		$image_title = 		$attachment->post_title;
		$description = 		$attachment->post_content;
		$galleryImgURL = 	wp_get_attachment_image_src( $id, 'medium', false );
		$galleryImgURL = 	$galleryImgURL[0];
		$galleryThumb = 	wp_get_attachment_image_src( $id, 'thumbnail', false);
		$galleryThumb = 	$galleryThumb[0];
		$fullscreenURL = 	wp_get_attachment_image_src( $id, 'large', false);
		$fullscreenURL = 	$fullscreenURL[0];

		$output .= '<a href="' . $galleryImgURL. '"><img src="' . $galleryThumb . '" data-big="' . $fullscreenURL . '" data-title="' . $image_title . '" data-description="' . $description . '"></a>';
	}

	$output .= '</div>';
	return $output;

}