Figure 1.
Schematic of how XCOR, LK and DDE calculate two-dimensional deformation gradient tensors. (a) Original test image (left) and warped image (right). (b) Rigid registration yields errors due to a parallelogram fit of the midpoints of a minimum of four regions (red boxes). (c) The LK method improves on this, but errors and reduced precision remain due to the parallelogram fit of the midpoints to calculate F (blue boxes). (d) DDE accurately calculates the deformation of all four regions independently (green boxes). Black borders: matched regions; dotted borders: calculated deformations for XCOR (red), LK (blue) and DDE (green). F, deformation gradient tensor; γ, shear strain; λ, stretch ratio in y direction; εα,x, error in α strain.