Most WordPress themes these days make use of Post Thumbnails or Featured Images as they are also called - these are one image that you associalte with your blog post which can be used in various sizes around your theme - the size and amount of thumbnails that are set is based on what your theme specifies. If you change to a different theme at a later date you will see that the thumbnail images are distorted - being stretched or compressed depending on the new theme's sizes.
Im in the process of moving a blog to a new theme and needed a way to regenerate the thumbnails for the new theme, I found a free plugin which will automate this process called Regenerate Thumbnails, lets take a look at how to use it.
Download Regenerate Thumbnails Here »
Install The Plugin
Download the plugin, then in your WordPress admin, visit “Plugins” > “Add New” > “Upload” and upload the file.
Resize Images
To resize featured images indivually, in your WordPress admin visit "Media" > "Library" and you will see all your uploaded images listed - if you hover over them you will see a "Regenerate Thumbnails" link appear :
On this page, you can also tick the checkboxes next to images and then from the "Bulk Actions" drop down box, again choose "Regenerate Thumbnails" :
Finally, to regenerate all thumbnails on your site at once, visit "Tools" > "Regen Thumbnails" and then click the "Regenerate Thumbnails" button :
The plugin will then start processing all the images and resaving them in the new size specified by your theme. This will take a while if you have a lot of posts, it took around 5 minutes for my site with 100 posts but the plugin does display a percentage progress meter :
Conclusion
This is a nice and simple plugin that does exactly what is required - give it a go next time you change themes and need your thumbnails recreated.
8 thoughts on “Regenerate Post Thumbnails After a WordPress Theme Change”
Amazing… last time i did it one by one :(
Good solution Oliver.
How about regenerating embedded images which aren’t thumbnails?
I think this one can regenerate all images – http://wordpress.org/extend/plugins/simple-image-sizes/
Hey Oli,
Have you seen this plugin work across the board? I know I tried it almost a year ago on a Genesis (child) theme that would not cooperate. I gave up on it then. I haven’t tried it since. Thanks for the reminder. I’ll give it another try on some other themes.
I havent tested with Genesis but I dont see why it wouldnt work it
Tried Simple Image Sizes plugin on a local installation which didn’t finish the job and found this plugin better Regenerate Thumbnails
This looks great Oli – I was hesitant about redesigning a blog of my right away because of this very reason. How do the images look after they have been resized?
I recently released a plugin that detects whenever your image sizes have changed and reminds you to regenerate them http://nextgenthemes.com/plugins/regenerate-thumbnails-reminder/ i hope this is useful to someone else too.
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