It's all about asking the right question...

Original question that has had me stuck for years: "How do you load landscape images as landscape and not portrait? (some sort of default, always loads it with the longer dimension vertically).

A new insight that I got today while using one of these apps: "How can I rotate an image after it's loaded?"

Very easy apparently...
As long as you keep track of the current angle, just reload and set a Rotation property to (current + 90) % 360...