recreating thumbnail images

Hi all,

We are currently running version 2.15 for listing clients holiday accommodation, due to a site rewrite we now require the thumbnail images created when the clients upload all their images to be a different size (larger) can someone please advise whether there is a way that we can re process all the client images to create thumbnails of the required sizes.

It wouldn't be professional to request all the advertisers to re-upload all their images and at a pinch we could I  suppose download all the uploaded images and convert create thumbnails manually but then I wouldn't know how to get those details into the database to be usable.

At present when images are uploaded the settings in cmsb resizes all images larger than 800 wide and 600 high and creates three thumbnails of differing sizes leaving the 4th one vacant.

I have noticed that there is a "recreate" button next to the thumbnail settings within the input validation section for the uploads in the section editor but I have no idea whether that just recreates the settings or physically recreates the thumbnail images. I don't want to mess with anything without being certain of what I am doing so if someone could clarify things for me it would be appreciated.

Thanks in advance for any help provided.