Let me explain â Until now, I have been using NextGen Gallery, and since I have a redesigned website that has image.php template (gallery attachments page), I would like to use WordPress’ built-in gallery feature instead.
Here’s the problem â I can’t forever continue to monitor if NextGen Gallery plugin is working as intended on my website, even though my old posts still use it.
Considering that, I would like to import and convert all NextGen galleries into WordPress galleries.
Is there a way to do this without all the hard work of having to upload gallery-by-gallery, post-by-post (I have close to 250 galleries!)?
Konstantin Kovshenin from Automattic built a small WP plugin hosted here at GitHUB, which does pretty much exactly what you are asking for.
It does not seem to solve the whole migration as it works only for
[nggallery]shortcodes, but anyone can fork it and add some more lines to solve the rest, right?Yes, it is entirely possible (and in fact, I am in the process of doing the same conversion).
[gallery]shortcode in the static Page content.Inserting uploaded images as attachments
The tricky part, of course, is Step #2. One option is the Add From Server Plugin, which inserts uploaded files as attachment post-types. If you use this Plugin, simply edit the static Page in question, click the “Upload/Insert” button, and then click the “Add From Server” tab.
Caveat: as far as I know, there is no good way to migrate your image metadata – such as captions – via the Add From Server Plugin, or any other similar method. You will likely have to recreate these data manually.
Regenerating Thumbnails
There are plenty of Plugins to accomplish this step. Just search the Plugin repo for “Regenerate thumbnails“
If you know sql convert, you can export sql to convert wp_ngg_pictures table’s data into wp_posts’ format.