If I Regenerate Thumbnails, would WordPress delete the existing Thumbnails and replace them with 'new copies'?

Question

I am currently working on a website, which has 1,000's of Product Images. All of these images were uploaded, without being optimized accordingly. For instance, most of the Product Images were uploaded with 5000px by 3000px dimensions which is far too large.

I have downloaded these Product Images to my computer, to start resizing them. Rather than manually do this, as it would simply take forever, I have setup my Photoshop to automate all of the resizing for me.

Furthermore, it would take forever to sift through the various Folders, as to pull out the original images to resize.

Instead, I was hoping to simply get Photoshop to resize every single Product Image in all of the Folders by 600px by 400px. Of course, this would also resize the various Thumbnail Images as well as the other image sizes WordPress creates upon the original image being uploaded.

Could I simply use the above approach, transfer the images back to WordPress via FTP and as long as I keep the file names the same for the various resizes images that WordPress creates, could I simply select 'Regenerate Thumbnails' and would WordPress delete their own resized images (which would now be 600px by 400px) and then replace them all with the correct sizes of 150px by 150px and 250px by 250px etc?

Answer 1

Here's what you can do:

Delete the Old Thumbnails

Download and install the Thumbnail Cleaner plugin. This plugin will delete all of your current thumbnails. You can do this manually by writing a PHP snippet that detects thumbnails and deletes them, but it's not really that necessary.

Resize the Original Images

Once you have deleted the thumbnails, copy what remains of your uploads to your computer. Then, use PhotoShop's automate feature to resize them all. Upload the folder back to your host, and overwrite everything. Ofcource, make a back-up first.

Regenerate New Thumbnails

After all the above is done, download and install the Regenerate Thumbnails by Viper00Bond, and create fresh thumbnails of your images.

Note:

Neither WordPress nor WooCommerce use the original images as product images or thumbnails. Unless you have no thumbnail at all ( which results in the original image being loaded ), there is no need to resize the original images.