XnView Software

I feel sheepish asking such a basic question, but I have mucked around trying to create a thumbnail in ver 1.61 and I can't understand what is going on.

I want to post a thumbnail on a message board of an image that is 900 X 658 X 24. Preferably I would like it about 25% of the original, but any ...

I know how to crop a rectangle.

Can I crop an irregularly sized object, such as a face, so I can brighten it and adjust it's color?