fn draw_star_mut<I>(image: &mut I, hist: &[f32], signed: bool)
where
    I: GenericImage<Pixel = Luma<u8>>,
{
    let orientations = hist.len() as f32;
    for bucket in 0..hist.len() {
        if signed {
            let dir = (2f32 * f32::consts::PI * bucket as f32) / orientations;
            let intensity = Clamp::clamp(hist[bucket]);
            draw_ray_mut(image, dir, Luma([intensity]));
        } else {
            let dir = (f32::consts::PI * bucket as f32) / orientations;
            let intensity = Clamp::clamp(hist[bucket]);
            draw_ray_mut(image, dir, Luma([intensity]));
            draw_ray_mut(image, dir + f32::consts::PI, Luma([intensity]));
        }
    }
}
Draws a visualisation of a histogram of edge orientation strengths as a collection of rays
emanating from the centre of a square image. The intensity of each ray is
proportional to the value of the bucket centred on its direction.
src/hog.rs