what model s7 do you have?

 

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).

 

If you were using Google photos, this wouldn't be an issue

 

edit: ^^^^^^this^^^^ (ninja'd)
also going forward i would recommend that you use google photos. it backs up your photos to the cloud. i never have to worry about my photos as it is saved in the cloud and i have access to it anytime i want. it also makes upgrading so much easier. it also save space on your sd card.

 

Install Twrp recovery

 

it will depend on what model s7 it is. if it is a snapdragon, its not that easy which is why we asked about the model of phone the op has.