Hough Transform - Voting

hough_transform_voting.rs

// calculate the longest line that can occur in the image (hypotenuse)
let max_line_length = (img_width as f64).hypot(img_height as f64).ceil();

// Create the accumulator matrix, x-axis is angle theta, y-axis is distance rho
let mut accumulator: na::DMatrix<u64> = na::DMatrix::new_zeros(180, max_line_length as usize);

// Flip y axis when reading image, as the image has 0/0 at the top left,
// but it's easier for us to work with when the origin 0/0 is at the bottom left
for y in 0..img_height {
    for x in 0..img_width {
        if !detect_edge(x, y_flipped) {
            continue;
        }

        for i in 0..3 {
            let theta = (i as f64 + 1.0) * 30.0;

            let rho = (x as f64) * theta.to_radians().cos() + (y_flipped as f64) * theta.to_radians().sin();
            let rho_rounded = rho.round();

            accumulator[(theta as usize, rho_rounded as usize)] += 1;
        }
    }
}