understrap/inc/bootstrap-wp-gallery.php

<?php
//Based on Jeff Hays code and his article here: http://robido.com/wordpress/wordpress-gallery-filter-to-modify-the-html-output-of-the-default-gallery-shortcode-and-style/
// Custom filter function to modify default gallery shortcode output
function bootstrap_wp_gallery( $output, $attr ) {


  // Initialize
  global $post, $wp_locale;

  // Gallery instance counter
  static $instance = 0;
  $instance++;

  // Validate the author's orderby attribute
  if ( isset( $attr['orderby'] ) ) {
    $attr['orderby'] = sanitize_sql_orderby( $attr['orderby'] );
    if ( ! $attr['orderby'] ) unset( $attr['orderby'] );
  }

  // Get attributes from shortcode
  extract( shortcode_atts( array(
    'order'      => 'ASC',
    'orderby'    => 'menu_order ID',
    'id'         => $post->ID,
    'itemtag'    => 'div',
    'icontag'    => 'div',
    'captiontag' => 'div',
    'columns'    => 3,
    'size'       => 'thumbnail',
    'exclude'    => ''
  ), $attr ) );

  // Initialize
  $id = intval( $id );
  $attachments = array();
  if ( $order == 'RAND' ) $orderby = 'none';


  if ( ! empty( $include ) ) {

    // Include attribute is present
    $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 ) );

    // Setup attachments array
    foreach ( $_attachments as $key => $val ) {
      $attachments[ $val->ID ] = $_attachments[ $key ];
    }

  } else if ( ! empty( $exclude ) ) {

    // Exclude attribute is present
    $exclude = preg_replace( '/[^0-9,]+/', '', $exclude );

    // Setup attachments array
    $attachments = get_children( array( 'post_parent' => $id, 'exclude' => $exclude, 'post_status' => 'inherit', 'post_type' => 'attachment', 'post_mime_type' => 'image', 'order' => $order, 'orderby' => $orderby ) );
  } else {
    // Setup attachments array
    $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 '';

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

  // Filter tags and attributes
  $itemtag = tag_escape( $itemtag );
  $captiontag = tag_escape( $captiontag );
  $columns = intval( $columns );
  $itemwidth = $columns > 0 ? floor( 12 / $columns ) : 100;
  $float = is_rtl() ? 'right' : 'left';
  $selector = "gallery-{$instance}";

 // Filter gallery CSS
  $output = apply_filters( 'gallery_style', "

    <div class='gallery galleryid-{$id} row'  id='$selector'>"
  );

  // Iterate through the attachments in this gallery instance
  $i = 0;
  foreach ( $attachments as $id => $attachment ) {

    // Attachment link
    $link = isset( $attr['link'] ) && 'file' == $attr['link'] ? wp_get_attachment_link( $id, $size, false, false ) : wp_get_attachment_link( $id, $size, true, false );

    // Start itemtag
    $output .= "<{$itemtag} class='gallery-item col-md-{$itemwidth}'>";

    // icontag
    $output .= "
    <{$icontag} class='gallery-icon'>
      $link
    </{$icontag}>";

    if ( $captiontag && trim( $attachment->post_excerpt ) ) {

      // captiontag
      $output .= "
      <{$captiontag} class='gallery-caption'>
        " . wptexturize($attachment->post_excerpt) . "
      </{$captiontag}>";

    }

    // End itemtag
    $output .= "</{$itemtag}>";

    // Line breaks by columns set
    if($columns > 0 && ++$i % $columns == 0) $output .= '<br style="clear: both">';

  }

  // End gallery output
  $output .= "
    <br style='clear: both;'>
  </div>\n";

  return $output;

}

// Apply filter to default gallery shortcode
add_filter( 'post_gallery', 'bootstrap_wp_gallery', 10, 2 );