Is there a way to make Irfanview AUTOCROP when it's a situation that isn't
too hard for an algorithm to figure out that there are black lines along
the outside of a set of photos?

Irfanview has a great batch facility on Windows, but the crop seems to be
manual.

Irfanview crops super easy, but usually, when I crop manually, I'm off by a
few pixels.

If not irfanview, what else free and simple might have a good manual or
batch autocrop?