In this paper we propose a framework for gradient descent
image alignment in the Fourier domain. Specifically,
we propose an extension to the classical Lucas & Kanade
(LK) algorithm where we represent the source and template
image’s intensity pixels in the complex 2D Fourier domain
rather than in the 2D spatial domain. We refer to this approach
as the Fourier LK (FLK) algorithm. The FLK formulation
is especially advantageous, over traditional LK,
when it comes to pre-processing the source and template images
with a bank of filters (e.g., Gabor filters) as: (i) it can
handle substantial illumination variations, (ii) the inefficient
pre-processing filter bank step can be subsumed within
the FLK algorithm as a sparse diagonal weighting matrix,
(iii) unlike traditional LK the computational cost is invariant
to the number of filters and as a result far more efficient,
(iv) this approach can be extended to the inverse compositional
form of the LK algorithm where nearly ...