WordPress: Native Gallery Paginated

function gallery_with_pagination($attr) {
    global $post;

    static $instance = 0;
    $instance++;

    extract( shortcode_atts( array(
        'qty' => '5'
    ), $attr ) );

    $imagesPerPage = $qty;

    // Define some default options
    $options = array(
        'order'=> 'ASC',
        'orderby'=> 'menu_order ID',
        'itemtag'=> 'dl',
        'icontag'=> 'dt',
        'captiontag'=> 'dd',
        'columns'=> 3,
        'size'=> 'thumbnail',
        'perpage'=> $imagesPerPage,
        'link'=>'attachment',
        'show_edit_links'=>'Y',
        'use_shortcode'=>'gallery',
        'exclude'=>''
    );

    // 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'] );
    }

    // Overwrite the defaults with any options passed in
    if (is_array($attr)) $options = array_merge($options, $attr);

    // Start by getting the attachments
    $attachments = get_children(array(
        'post_parent'=> $post->ID,
        'post_status'=>'inherit',
        'post_type'=> 'attachment',
        'post_mime_type'=>'image',
        'order'=> $options['order'],
        'orderby'=> $options['orderby'],
        'exclude'=> $options['exclude']
    ));

    // If we don't have any attachments - output nothing
    if ( empty($attachments) ) return '';

    // Output feed if requested
    if ( is_feed() ) {
        $output = "\n";

        foreach ( $attachments as $id => $attachment )
            $output .= wp_get_attachment_link($id, $options['size'], true) . "\n";
        return $output;
    }

    // Standard post output

    // Work out how many pages we need and what page we are currently on
    $imageCount = count($attachments);
    $pageCount = ceil($imageCount / $imagesPerPage);

    $currentPage = intval($_GET['galleryPage']);
    if ( empty($currentPage) || $currentPage<=0 ) $currentPage=1;

    $maxImage = $currentPage * $imagesPerPage;
    $minImage = ($currentPage-1) * $imagesPerPage;


    if ($pageCount > 1)
    {
        $page_link= get_permalink();
        $page_link_perma= true;
        if ( strpos($page_link, '?')!==false )
            $page_link_perma= false;

        $gplist= '<div class="gallery_pages_list">'.__('Pages').'&nbsp; ';
        for ( $j=1; $j<= $pageCount; $j++)
        {
            if ( $j==$currentPage )
                $gplist .= '<strong class="current_gallery_page_num"> '.$j.' </strong>&nbsp;';
            else
                $gplist .= '<a href="'.$page_link. ( ($page_link_perma?'?':'&amp;') ). 'galleryPage='.$j.'">'.$j.'</a>&nbsp; ';
        }

        $gplist .= '</div>';
    }
    else
        $gplist= '';

    $itemtag = tag_escape($options['itemtag']);
    $captiontag = tag_escape($options['captiontag']);
    $columns = intval($options['columns']);
    $itemwidth = $options['columns'] > 0 ? floor(100/$options['columns']) : 100;
    $float = is_rtl() ? 'right' : 'left';
    $icontag = $options['icontag'];
    $id = isset($options['id']) ? $options['id'] : '';
    $size = $options['size'];

    $selector = "gallery-{$instance}";

    $gallery_style = $gallery_div = '';
    if ( apply_filters( 'use_default_gallery_style', true ) )
        $gallery_style = "
        <style type='text/css'>
            #{$selector} {
                margin: auto;
            }
            #{$selector} .gallery-item {
                float: {$float};
                margin-top: 10px;
                text-align: center;
                width: {$itemwidth}%;
            }
            #{$selector} img {
                border: 2px solid #cfcfcf;
            }
            #{$selector} .gallery-caption {
                margin-left: 0;
            }
        </style>
        <!-- see gallery_shortcode() in wp-includes/media.php -->";
    $size_class = sanitize_html_class( $size );
    $gallery_div = "<div id='$selector' class='gallery galleryid-{$id} gallery-columns-{$columns} gallery-size-{$size_class}'>";
    $output = apply_filters( 'gallery_style', $gallery_style . "\n\t\t" . $gallery_div );

    $i = 0;
    $k = 0;
    foreach ( $attachments as $id => $attachment ) {
        if ($k >= $minImage && $k < $maxImage) {
            $link = isset($options['link']) && 'file' == $options['link'] ? wp_get_attachment_link($id, $size, false, false) : wp_get_attachment_link($id, $size, true, false);

            $output .= "<{$itemtag} class='gallery-item'>";
            $output .= "
                <{$icontag} class='gallery-icon'>
                    $link
                </{$icontag}>";
            if ( $captiontag && trim($attachment->post_excerpt) ) {
                $output .= "
                    <{$captiontag} class='wp-caption-text gallery-caption'>
                    " . wptexturize($attachment->post_excerpt) . "
                    </{$captiontag}>";
            }
            $output .= "</{$itemtag}>";
            if ( $columns > 0 && ++$i % $columns == 0 )
                $output .= '<br style="clear: both" />';
        }
        $k++;
    }
    $output .= "\n<br style='clear: both;' />$gplist\n</div>\n";

    return $output;

    // If we've got this far then we must have some attachments to play with!
    //return 'Gallery Here - Page '. $currentPage. ' de '. $pageCount;
}

add_shortcode('page-gallery', 'gallery_with_pagination');