For instance: If you move the mouse up it scrolls the image downwards, likewise if you move the mouse left it would pan the image right. All this without needing to sustain and hold a mouse button.
Overall it's quite similar to an inverted middle mouse button "scroll mode" seen in most web browsers and without the annoying cursor arrows/indicators. It feels much more intuitive then it sounds.

Basically I would like to see such a feature in Xnview:
At a button press Xnview would enter a "scroll follows mouse mode" wherein the image follows and moves along with the mouse in inverted fashion (as mentioned above) until the button is pressed again to toggle it off.
Thanks!