What are some various ways an iPhone will save a photo as .png?

[iMore Question]

Various ways an iPhone will save a photo as .png

iphone5
What are the various ways an iPhone will save a photo as a .png file?
Basically, I have a photo which has the .png file extension. Could the fact that it is a crop from an original photo cause the phone to save it as .png?
Thanks

 

[kch50428]

Re: Various ways an iPhone will save a photo as .png

The camera app saves as jpg as far as I know... something that's png would have had to have been modified by an app and the app saved it as such.