;\begin{verbatim} ;+ ; NAME: aligninv ; PURPOSE: Get an inversion alignment structure ; CALLING SEQUENCE: ; B = aligninv(A) ; INPUT: ; A an alignment structure, representing the mapping ; (l,m) ----> (i,j) ; OUPUT: ; B the inversion alignment structure, representing ; the mapping (i,j) ---> (l,m) ;- b=alignstr() b.object = a.reference b.reference = a.object b.ref_origin= a.obj_origin b.obj_origin= a.ref_origin b.ref_aspect = a.obj_aspect b.obj_aspect = a.ref_aspect b.flip = a.flip b.scale = 1./a.scale b.rotation = -a.flip(0)*a.flip(1)*a.rotation return, b end ;\end{verbatim}