the Decomposition of
  Deformations&quot;.  Bookstein.  PAMI 1989.

 USAGE
  [warp,L,LnInv,bendE] = tpsGetWarp( lambda, xsS, ysS, xsD, ysD )

 INPUTS
  lambda      - rigidity of warp (inf means warp becomes affine)
  xsS, ysS    - [1xn] correspondence points from source image
  xsD, ysD    - [1xn] correspondence points from destination image

 OUTPUTS
  warp        - bookstein warping parameters
  L, LnInv    - see bookstein
  bendE       - bending energy

 EXAMPLE - 1
  xsS=[0 -1 0 1];  ys