change-gallery-output-caption.php

<?php 
/* 
 * Change WordPress default gallery output
 * http://wpsites.org/?p=10510/
 */
add_filter('post_gallery', 'ct__post_gallery', 10, 2);
function ct_post_gallery($output, $attr) {
global $post;
 
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];
    }
}
 
if (empty($attachments)) return '';
 
// Here's your actual output, you may customize it to your need
$output = "<div class=\"slideshow-wrapper\">\n";
$output .= "<div class=\"preloader\"></div>\n";
$output .= "<ul data-orbit>\n";
 
// Now you loop through each attachment
foreach ($attachments as $id => $attachment) {
    // Fetch all data related to attachment 
    $img = wp_prepare_attachment_for_js($id);
 
    // If you want a different size change 'large' to eg. 'medium'
    $url = $img['sizes']['large']['url'];
    $height = $img['sizes']['large']['height'];
    $width = $img['sizes']['large']['width'];
    $alt = $img['alt'];
 
    // Store the caption
    $caption = $img['caption'];
 
    $output .= "<li>\n";
    $output .= "<img src=\"{$url}\" width=\"{$width}\" height=\"{$height}\" alt=\"{$alt}\" />\n";
 
    // Output the caption if it exists
    if ($caption) { 
        $output .= "<div class=\"orbit-caption\">{$caption}</div>\n";
    }
    $output .= "</li>\n";
}
 
$output .= "</ul>\n";
$output .= "</div>\n";
 
return $output;
}
;?>

change-gallery-output.php

<?php 
/* 
 * Change WordPress default gallery output
 * http://wpsites.org/?p=10510/
 */
add_filter('post_gallery', 'ct_post_gallery', 10, 2);
function ct_post_gallery($output, $attr) {
    global $post;
 
    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];
        }
    }
 
    if (empty($attachments)) return '';
 
    // Here's your actual output, you may customize it to your need
    $output = "<div class=\"slideshow-wrapper\">\n";
    $output .= "<div class=\"preloader\"></div>\n";
    $output .= "<ul data-orbit>\n";
 
    // Now you loop through each attachment
    foreach ($attachments as $id => $attachment) {
        // Fetch the thumbnail (or full image, it's up to you)
//      $img = wp_get_attachment_image_src($id, 'medium');
//      $img = wp_get_attachment_image_src($id, 'my-custom-image-size');
        $img = wp_get_attachment_image_src($id, 'full');
 
        $output .= "<li>\n";
        $output .= "<img src=\"{$img[0]}\" width=\"{$img[1]}\" height=\"{$img[2]}\" alt=\"\" />\n";
        $output .= "</li>\n";
    }
 
    $output .= "</ul>\n";
    $output .= "</div>\n";
 
    return $output;
}
;?>

add_filter('post_gallery', 'ct__post_gallery', 10, 2); function ct_post_gallery($output, $attr)

Function name should be "ct__post_gallery"