The original file name was called ‘Screen_151114_161146.png’ so when we try to rename it (perhaps a file name length bug in a PNG processing lib?) then ‘a.png’ will also fail. Thinking that Discourse might have a duplicate image check, we altered a pixel and saved the rename and it now seems to work. A clue, or just a side effect of resaving in Win10 Paint rather than the name?
EDIT2: Further digging into the byzantine world of PNG encoding. Bad file:
.\Screen_151114_161146.png file doesn't end with an IEND chunk
So, not sure that this is a Discourse issue at all. If RMagik is being being used, which eventually gets to libpng then the convert is not going to be able to open. The chances of that flight sim fixing a bug in their screenshot generation feature is pretty slim, which is unfortunate as we’re a flight sim forum.
EDIT3: Yep, looks like it is failing silently here on the convert binary call: