What is this odd symbol showing on the lower left corner on a single photo in my S4's photo gallery?

[AC Question]

On my Galaxy S4, one of the pictures in my photo gallery (in the folder that has photos received from Whatsapp), has a strange white symbol on its lower left corner that I have never seen before. It's hard to describe, but it kinda looks like a three part mirror viewed from the front, with the outer "mirrors" or "wings" angled slightly forward and towards the middle one. It's only on this one photo. What is this symbol?

 

[belodion]

Panorama?