Unfortunately, computation of appropriate registration parameters
is complicated. Even the simplest models must first nominate
features that are invariant between known-match images. Clearly
minutiae coordinates (x, y) will vary between mis registered
known-matches, so automated algorithms must seek alternative
features (or alternative means) of deducing correspondences. One
approach to this problem is to generate Delaunay triangles using
minutiae as vertices (Fig. 1) [12]. Ideally, minutia triplets generate
triangles that possess invariant features (inner angles and ratio of
sides) which in turn nominate a series of candidate control points
that can be used to compute the registration parameters that
maximize the similarity between two images [11,12].