My friend showed me her S4 mini, she has a problem with the back camera where the image is completely black except for purple lines across the screen. An image with an example is attached. I've deleted the cache and data of the camera app, done a hard reset, tried a separate camera app, everything. The phone was not dropped, and has a flip case that protects it well.
She had this problem before but it fixed itself, but now she needs her camera for an event and wants to make sure it's fixed.