Whether it's possible or not will depend on which model of Galaxy S7 you have (e.g. US carrier-locked models are different from European unlocked ones).
But it probably doesn't matter anyway: that device was released with Android 6, so the storage will have been encrypted by default. A reset will erase the encryption key, so even if you could recover the files you couldn't decrypt them. So I think it's unlikely you'll be able to recover the images anyway.
It's important to always have a backup of anything important, I'm afraid. Look at it this way, what would you do if the phone was lost or stolen? Or if it (or the SD card) broke.
(On that last aside, if the images were stored on a removable SD card that won't be encrypted: you can just stick it in a card reader, attach it to a computer, and run any file recovery software you like. But if they were on the internal storage I think they are gone).
