Frangi¶
The Frangi vesselness filter combines the Hessian’s two eigenvalues into a single response that’s large for elongated, tube-like structures and small for blob-like or flat regions — originally designed to enhance blood vessels in medical images, but equally applicable to any tubular or filamentary structure (cracks, fibers, grain boundaries). Running it across a range of scales lets it respond to tubes of different widths in the same image.
See also
Hessian — the eigenvalue analysis Frangi’s response is built from
Meijering, Sato — alternative vesselness/tubeness filters with different eigenvalue-combination formulas
Feature Extraction — every other feature