Region-based
Feature Measures
φ3(s)
= dist(s, ψ(s))
Measures
proximity of paired linelets across a
region
φ4(s)
= φ3'(s), the derivative
φ4(s)
= 0 implies paired linelets are parallel
φ5(s)
= φ'4(s)
= φ3''(s)
φ5(s)
= 0 implies paired linelets are symmetric