Add a new "Image" transform type to the transform tools, in
addition to the existing "Layer", "Selection", and "Path" transform
types.  The "Image" mode transforms the entire image, rather than a
single item.  In tools with a preview, the preview shows the
transformed image projection.  The clipping mode controls how the
canvas is clipped during the transform; in particular, the ADJUST
clipping mode resizes the canvas to fit its transformed size.