Function fast_corner_score

pub fn fast_corner_score(
    image: &GrayImage,
    threshold: u8,
    x: u32,
    y: u32,
    variant: Fast,
) -> u8

The score of a corner detected using the FAST detector is the largest threshold for which this pixel is still a corner. We input the threshold at which the corner was detected as a lower bound on the search. Note that the corner check uses a strict inequality, so if the smallest intensity difference between the center pixel and a corner pixel is n then the corner will have a score of n - 1.