“…A practical choice for {f j (x,y)} is the set of bivariate polynomials. 8,20 The first three terms, {f 0 (x,y) = 1, f 1 (x,y) = x, f 2 (x,y) = y}, give the set of all possible linear transformations, which includes translation, rotation, skew, and scaling. Nonlinear transformations that correct for deformations can be made by including second-order terms:…”