I'm on Isa 2
Unfortunatley the Matte actors in Isadora 2 have a bug related to the 'scale fg' function, that makes it so I can't port this User Actor backwards to Isadora 2.
Here are the guts of the user actor in case its useful for anyone else to understand.
The basics are that the image is placed onto (using Matte++) a Square canvas (using the greater of Width or Height).
Then the square canvas is rotated 90, 180, 270 degrees (as needed). Finally the Square canvas is cropped back down to the image size.