How to reverse mirrored images?

I've used Photo Booth to photo pages from books in libraries. Then I've exported some of these images (often not in normal position) and deleted them from Photo Book. And then I found out about the mirroring of the photos in Photo Book.

Any ideas of what I should do? I can't find a way to import them into Photo Book and other image programmes I've tried gives me the opportunity to reverse left or right or…. But I haven't found any way to reverse mirroring. Reading mirrored text is hard, worse than upside down. Help!

I have no idea what Photo Book is, so I can't help you with that.

You could open the image in Preview and "flip horizontal," which should fix the issue.

Thank you!
It worked!