ギャラリーのショートコード「exclude」が効かない

初めて質問させて頂きます。

graphpaperpress.comというところの、
「Retouch Pro」（※デモページ）
というテーマを使っています。

このテーマには投稿フォーマットが「標準」「投稿」「ギャラリー」とあるんですが、
この中でフォーマットを「ギャラリー」と設定した時に、
デフォルトのショートコード「exclude」が機能してくれません。

そもそもPHPのことが殆ど分からないので、
functions.phpでオーバーライドしている、のかな、くらいの見当しかつきません。
私はただ、[gallery exclude='画像ID']をきちんと機能させたいだけなのですが、
何をどうすればよいのか、教えて頂けますでしょうか？

以下、コードを転載します。
何卒よろしくお願いします。

functions.php

//hide gallery shortcode
function gpp_the_gallery_content($content) {
	global $post_id;
	$format = get_post_format($post_id);
	if ($format == 'gallery') {
		$content = strip_shortcodes($content);
		return $content;
	} else {
		return $content;
	}
}
add_filter('the_content', 'gpp_the_gallery_content');

add_shortcode('gallery', 'gpp_retouch_gallery_shortcode');

/**
 * The Gallery shortcode.
 */
function gpp_retouch_gallery_shortcode($attr) {
	global $post;

	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);
	$itemwidth = $columns > 0 ? floor(100/$columns) : 100;
	$float = is_rtl() ? 'right' : 'left';

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

	$gallery_style = $gallery_div = '';

	$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;
	$j=0;
	foreach ( $attachments as $id => $attachment ) {

		if ( $columns > 0 && ++$i % $columns == 0 ) {
			$class = " last";
		} else {
			$class = "";
		}

		$link =  wp_get_attachment_image($id, $size, 0); 

		$output .= "<{$itemtag} class='gallery-item" . $class . "'>";
		$output .= "
			<{$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}>";

	}

		$output .= "<div id='ph'></div><div id='lnav'>Left</div><div id='phbox'>";
		foreach ( $attachments as $id => $attachment ) {
			$output .= '<div class="mainimgcontainer '.$j.'">';
			$output .= '<div class="imgcontainer">';
			$output .= wp_get_attachment_image($id, "large", 0);
			$output .= '</div>';
			if($attachment->post_excerpt == "" && post_exif($id) == "" ){

			} else {
				$output .= '<div class="gallery-exif">';
				$output .= '<span class="g-caption">'.$attachment->post_excerpt.'</span>';
				$output .= '<div class="galexif-content">';
				$output .= post_exif($id);
				$output .= '</div></div><div class="g-exif-info">info</div>';
			}
			$output .= '<div class="clear"></div></div>';
			$j++;
		}
		$output .= "</div><div id='rnav'>Right</div>\n";

	$output .="<div class='clear'></div>";
	$output .= "</div>\n";

	return $output;
}

function dec2frac($dec) {
	global $result;
	$count = 0;
	$result = array();
	decimalToFraction($dec, $count, $result);
	$count = count($dec);
	return simplifyFraction($result,$count,1,$result[$count]);
}

function decimalToFraction($decimal,$count,$result) {
	global $result;
    $a = (1/$decimal);
    $b = ( $a - floor($a)  );
    $count++;
    if ($b > .01 && $count <= 5) decimalToFraction($b,$count,$result);
    $result[$count] = floor($a);
}
function simplifyFraction($fraction,$count,$top,$bottom) { 

	if($count>1){
		$next = $fraction[$count-1];
	} else {
		$next = "";
	}

    $a = ($bottom * $next) + $top;
    $top = $bottom;
    $bottom = $a;
    $count--; 

    if ($count > 0) simplifyFraction($fraction,$count,$top,$bottom);
    else {
        return "$bottom/$top";
    } 

}

content-gallery.php（投稿フォーマット　※デフォルトから少し触ってます）

<article id="post-<?php the_ID(); ?>" <?php post_class(); ?>>
  <div id="collection" class="entry-content">
    <header class="entry-header">
      <h2 class="entry-title"><?php the_title(); ?></h2>
    </header>
    <!-- .entry-header -->
    <div class="post-thumbnail"><?php echo do_shortcode("[gallery columns='3']"); ?></div>
    <div class="clear"></div>
  </div>
  <!-- .entry-content -->

  <div class="meta-data"> <span class="info-meta"><a href="#content"><?php printf(__( 'product information','gpp_lang' )); ?></a></span>
    <?php if ( comments_open() || ( '0' != get_comments_number() && ! comments_open() ) ) : ?>
    <span class="comments-link">
    <?php comments_popup_link( __( 'Leave a comment','gpp_lang' ), __( '1 Comment','gpp_lang' ), __( '% Comments','gpp_lang' ) ); ?>
    </span>
    <?php endif; ?>
  </div>
  <div id="info_content" class="main-content">
    <?php the_content(); ?>
  </div>
</article>
<!-- #post-<?php the_ID(); ?> -->