To
recover deleted photos from Samsung Galaxy S7, first stop using it in case of data overwritten. Then find a pro Samsung Photo Recovery software to get them back like this:
Step 1. Connect Samsung Galaxy to Computer (Enable USB Debugging)
If you sure the photos you want to restore are located in the external SD card, then there is no need for you to root your Samsung devices. Otherwise, you have to root your Samsung Galaxy so that the program can get access to your phone's internal flash card to scan the lost photos. After that, connect your Samsung Galaxy to computer and follow the below ways to open USB debugging:
1) For Android 2.3 or earlier: Enter "Settings" < Click "Applications" < Click "Development" < Check "USB debugging"
2) For Android 3.0 to 4.1: Enter "Settings" < Click "Developer options" < Check "USB debugging"
3) For Android 4.2 or newer: Enter "Settings" < Click "About Phone" < Tap "Build number" for several times until getting a note "You are under developer mode". Then you may back to "Settings" < Click "Developer options" < Check "USB debugging".
Step 2. Run the Program and Scan for Files
Launch the program on your computer and it will auto-detect the device that you've connected to the computer via USB cable. When the device is detected, the program will start scanning for files on your Samsung Galaxy immediately.
Step 3. Preview & Recovery
Click "Android UMS Com... " to expand the options in the left column, and then you can select the folder and preview all scanned photos in the right panel. Go through these pictures and find the one you need to restore, mark them. Then you can click "Recover" button to save them on your desktop computer.