You can save source quality using the Aloha browser (assuming android). Click on the pic, then I believe you should hold on the pic until a menu pops up to save it. That should get your source quality.
It's definitely easier on PC if that's possible. You can add the "Allow Right-Click" extension on Chrome (probably the same on FireFox). Click on the photo, then right-click to open in a new tab and save pic.