How to Edit an non-extension Picture?

I have an open source application that i can edit any files on it. Now i want to edit some pictures that have no Extension! (Just the picture name can shown). and when i open them with any Picture-Editors (like Paint, Ashampoo, GIMP), it says "Unknown Extension.". but i have to Edit this non-Extension picture

My Question:
How can i Edit an non-extension picture file?

Answer

First of all, ensure that the file isn't corrupted.

In Linux use file and in Windows use TrID to try and determine what format the file is.

Once you've done so you can add the appropriate extension and see if your viewers/editors are able to open it.