Figure 5.

(a) Locations of the four finger webs FW₁, FW₂, FW₃, and FW₄. Line $\overline{FS}$ is formed by FW₂ and FW₄. The angle θ is measured between line $\overline{FS}$ and a horizontal line; (b) The resulting image rotated with angle θ; (c) Location of the ROI.