This script extracts your photomode pictures from your save games folder and converts them to jpg. Simply run rdr2_photomode.py and a folder with your images will appear.
Install Python 3
You might need to adapt the path to your RDR2 save game folder. Edit rdr2_photomode.py and replace the path in this line:
dir = os.path.expanduser('~') + "\Documents\Rockstar Games\Red Dead Redemption 2\Profiles"
Have fun