Wraps regular post images with Divi Lightbox

divi-lightbox-for-regular-images.php

/* Add this into functions.php of child theme */

/* Wrap post images with links with Divi lightbox */
add_filter('the_content', 'divi_lightbox');
function divi_lightbox($content)
{
    global $post;
    $pattern = '#(<a.*href=".*\.(?:bmp|gif|jpeg|jpg|png)")(.*>.*<img.*>.*</a>)#i';
    $replacement = '$1 class="et_pb_lightbox_image" title="' . $post->post_title . '"$2';
    return preg_replace($pattern, $replacement, $content);
}