pub fn corners_fast9(image: &GrayImage, threshold: u8) -> Vec<Corner> {
    let (width, height) = image.dimensions();
    let mut corners = vec![];

    for y in 0..height {
        for x in 0..width {
            if is_corner_fast9(image, threshold, x, y) {
                let score = fast_corner_score(image, threshold, x, y, Fast::Nine);
                corners.push(Corner::new(x, y, score as f32));
            }
        }
    }

    corners
}
Finds corners using FAST-9 features. See comment on Fast enum.
src/corners.rs