Function compute_vesselness 

fn compute_vesselness(
    l1: f64,
    l2: f64,
    l3: f64,
    a: f64,
    b: f64,
    c2: f64,
    black_white: bool,
) -> f64

Compute vesselness measure from sorted eigenvalues |lambda1| <= |lambda2| <= |lambda3|