Thumbnail regeneration is not reversible, but you can just change your thumbnail dimensions back to the old values and click the button again if you don’t like the results.Thumbnail regeneration is not reversible, but you can just change your thumbnail dimensions back to the old values and click the button again if you don’t like the results.Thumbnail regeneration is not reversible, but you can just change your thumbnail dimensions back to the old values and click the button again if you don’t like the results.