Function rdp_simplify

crates/plotlars-plotters/src/render/mod.rs:275–301

Ramer-Douglas-Peucker polyline simplification.

(points: &[(f64, f64)], epsilon: f64)

/// Ramer-Douglas-Peucker polyline simplification.
fn rdp_simplify(points: &[(f64, f64)], epsilon: f64) -> Vec<(f64, f64)> {
    if points.len() <= 2 {
        return points.to_vec();
    }
    let first = points[0];
    let last = points[points.len() - 1];

    let mut max_dist = 0.0f64;
    let mut max_idx = 0;
    for (i, &p) in points.iter().enumerate().skip(1).take(points.len() - 2) {
        let d = perp_distance(p, first, last);
        if d > max_dist {
            max_dist = d;
            max_idx = i;
        }
    }

    if max_dist > epsilon {
        let mut left = rdp_simplify(&points[..=max_idx], epsilon);
        let right = rdp_simplify(&points[max_idx..], epsilon);
        left.pop();
        left.extend(right);
        left
    } else {
        vec![first, last]
    }
}

fn perp_distance((px, py): (f64, f64), (ax, ay): (f64, f64), (bx, by): (f64, f64)) -> f64 {
    let dx = bx - ax;