Original: https://gist.github.com/deltafactory/6789297

fix-nextgen-path

<?php
/*

INSTRUCTIONS:
Use at your own risk. Backup your database before continuing.

1. Copy code to a file in the root of your website.
2. Change YOUR_SITE_ROOT to a value that makes sense.
3. Execute by visiting the page. Verify before/after results.
4. Change MAKE_CHANGES_TO_SITE to true and execute it again.

*/

/*** Change this to the URL of your Wordpress installation, without the trailing slash. ***/
define( 'YOUR_SITE_ROOT', 'your.domain' );

define('FROM_ROOT', 'http://localhost/');

/*** When the results have been confirmed, change this to true to modify data. ***/
define( 'MAKE_CHANGES_TO_SITE', true );

/*** If your are using multisite, set the site ID ***/
define( 'SITE_ID', 1 );

/*** No need to edit below here. ***/

require( 'wp-load.php' );             // Load the WordPress environment
header( 'Content-type: text/plain' ); // Set text output for easier debugging/readability.
fix_ngg_lightbox();                   // Run the fix

function fix_ngg_lightbox() {
	global $wpdb;
	
	if(is_multisite())
	  switch_to_blog(SITE_ID);

	// Find the row in question, if it exists.
	$posts = $wpdb->get_results(
		"SELECT ID, post_title, post_content
		FROM $wpdb->posts
		WHERE post_type='lightbox_library'"
	);

	foreach($posts as $post) {
	
		if ( !$post )
			exit( 'Lightbox library post not found.' );

		// Decode blob to proper object. Done twice to avoid shared reference.
		$data_before = json_decode( base64_decode( $post->post_content ) );
		$data = json_decode( base64_decode( $post->post_content ) );
		foreach($data as &$v) {
			if(is_object($v) || is_array($v)) {
				foreach($v as &$v2) {
					$v2 = str_replace(FROM_ROOT, YOUR_SITE_ROOT, $v2);
				}
			}else {
				$v = str_replace(FROM_ROOT, YOUR_SITE_ROOT, $v);	
			}			
		}

	$post_content = $post_content_filtered = base64_encode( json_encode( $data ) );

	echo "\n\n";
	if ( MAKE_CHANGES_TO_SITE ) {
		$wpdb->update( $wpdb->posts, compact( 'post_content', 'post_content_filtered' ), array( 'ID' => $post->ID ) );
		echo '*** Done.';
	} else {
		echo '*** No data is being changed. Verify the results and change the constant "MAKE_CHANGES_TO_SITE" to "true" and re-run the script to commit.';
	}
	echo "\n\n";

	echo "Before:\n";
	print_r( $data_before );
	echo "\nAfter:\n";
	print_r( $data );
	}

}