Its a very easy way to zoom into pictures.
Suggestion:
When being in the fullimage view, you should be able to draw a rectangle on the image holding down a mousebutton and at the moment you let go of the mousebutton, the image is zoomed to fit that specific rectangle.
I could name another viewer that does that perfectly, but i dont want to advertise another viewer here. Besides it is not as good as xnview in every other aspect but this one.
Thanx to the xnview-team. <3