Suppose I have a VectorDistanceMap image, the pixel type
is Offset<3>, say <u(x,y,z),v(x,y,z),w(x,y,z)>. How do I
get the Jacobian of Offset?
    du/dx  du/dy  du/dz
    dv/dx  dv/dy  dv/dz
    dw/dx  dw/dy  dw/dz
Thanks!
-- 
Best wishes,
Bing Jian
bjian at cise . ufl . edu