So PixelCNC automatically scales a loaded image to fill the canvas while retaining its aspect ratio. So if your image is square (width and height are the same) then the layer will be scaled to the smallest canvas dimension, either X or Y. In the case of a canvas that's 24"x48" that would mean that a square image would be scaled to 24"x24".
I'm not sure I follow what you mean about the orientation and resizing. :P
- Charlie