WordPress 2.9 came with a number of nice new features, specifically the ability to assign thumbnails to posts, and to specify the size of those thumbnails by using functions like add_image_size() in your theme’s functions.php file. Unfortunately, add_image_size() isn’t backwards compatible, meaning that any images that were uploaded before the new sizes were created will not have a corresponding thumbnail. Instead, WordPress will grab the size that most closely matches the post thumbnail size, which is not always ideal.
I created a plugin called Thumbnail Updater to address this problem. Thumbnail Updater adds a button to the Edit Media page for each image that says “Update Image Sizes.” Just click the button to update your thumbnails—it can take a while depending on the size of the images and the server speed.
*new* Download: Thumbnail Updater 1.0
Download: Thumbnail Updater 0.1-beta
THIS IS A TEST YO