As I've said, I only needed it a couple of times. Quickly Googled "batch image convert rename linux" or sth like that, saw which tool(s) I can use, checked the man page and I was done. My point was that if it had a simple GUI, I wouldn't have to read the man page.

_Settling_ on a solution indicates that a task is performed more often. In such a case, CLI is perfectly fine, because you learn how to use it while you do it and this knowledge sticks after several uses. I haven't used IrfanView, but I doubt it can compete with all the goodness of the command line.