How to replace (not delete) image in gallery with a better version

Thanks for your attention!

I read information on how to delete and upload a new image in Nextgen, but cant find a solution for this: I was guessing a lot of people want to keep the title and ALT information and google indexing of an image, but still replace a photo with a better version (extra photoshopped for instance). [When i delete an image, upload a new version and put in the same information, links to that image are lost and google will not index it the same.]

How could i just replace the image in a gallery?

Thanks!