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I'm applying a new theme to my site, and the theme has a custom thumbnail size. I realize that add_image_size() does the work of creating the custom thumb whenever a new post is created.

This in my theme's functions.php:

add_image_size('ttrust_threeColumn', 280, 170, true);

However, I have a bunch of old posts I need to create this thumbnail size for. These old posts have a filename stored in a custom "Thumbnail" field, e.g.:


I can grab that file path with this:

get_post_meta($post->ID, 'Thumbnail')

Now if I loop through all the old posts, how can I create the custom ttrust_threeColumn thumbnail size for each post?

I appreciate the help! I've tried a bunch of different functions and methods, but I can't seem to get a grasp on thumbnail creation for existing posts.

share|improve this question
up vote 2 down vote accepted


Afaik add_image_size works for new IMAGES, and not for new posts, but regardless of this I think all you need to do is regenerate your thumbnails with the must-have "regenerate thumbnails" plugin.


share|improve this answer
That worked, thanks. I found Ajax Thumbnail Rebuild to be a little more user friendly and better performance-wise: wordpress.org/extend/plugins/ajax-thumbnail-rebuild – Banjer Jan 9 '12 at 14:28
awesome! thanks – Talbatz Jan 10 '12 at 11:29

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