NextGen Gallery singlepic images

I like this plugin a way more then WordPress-SEO for its’ simplicity and robustness. Unfortunately, XML-Sitemap is unable to list pictures posted through the NextGen Gallery plugin, on which my site is heavily relying. So I wrote a simple patch to enable it to handle the [singlepic] shortcode (at least). Maybe it will be usefull to someone:

xml-sitemap-feed/includes/core.php:
466			if('attached' == $which) {
467				$args = array( 'post_type' => 'attachment', 'post_mime_type' => 'image', 'numberposts' => -1, 'post_status' =>'inherit', 'post_parent' => $post->ID );
468				$attachments = get_posts($args);
469				if ($attachments) {
470					foreach ( $attachments as $attachment ) {
471						$url = wp_get_attachment_image_src( $attachment->ID, 'full' );
472						$this->images[$post->ID][] = array(
473										'loc' => esc_url( $url[0] ),
474										'title' => apply_filters( 'the_title_xmlsitemap', $attachment->post_title ),
475										'caption' => apply_filters( 'the_title_xmlsitemap', $attachment->post_excerpt )
476										);
477					}
478				}
				#check for NextGen singlepics
				if (class_exists('nggdb')) {
				    if (preg_match_all( '<code>\[singlepic id=[0123456789]+</code>', $post->post_content, $matches)) {
					    foreach ($matches[0] as $img) {
						    if (preg_match( '<code>=([0123456789]+)</code>', $img, $match)) {
							    $img = nggdb::find_image($match[1]);
							    $image = array('loc' => esc_url($img->imageURL),
							                    'title' => $img->alttext,
							                    'caption' => $img->alttext);
							    $this->images[$post->ID][] = $image;
						    }
					    }
    				}
    			}
			} elseif ('featured' == $which) {
				if (has_post_thumbnail( $post->ID ) ) {

*Note: <code> tags appearing in the snippet are actually backquotes transformed by the forum. They are part of regexps.

https://wordpress.org/plugins/xml-sitemap-feed/