[R-Cramer4]

Lines with angles less than 90 degrees were always beveled so this fix changes that behavior to use the miter limit.

Before

After

Code used for the images

use std::io::Write;
use zeno::{Join, Mask, Stroke};

const T: u32 = 240;

struct Case {
    path: String,
    limit: f32,
}

fn cases() -> Vec<Case> {
    let h = 160.0 * 3f32.sqrt() / 2.0;
    let tri = format!("M 120 40 L 200 {y} L 40 {y} Z", y = 40.0 + h);
    let mut star = String::new();
    for i in 0..5 {
        let a = -std::f32::consts::FRAC_PI_2 + i as f32 * 4.0 * std::f32::consts::PI / 5.0;
        star += &format!("{} {} {} ", if i == 0 { "M" } else { "L" }, 120.0 + 90.0 * a.cos(), 130.0 + 90.0 * a.sin());
    }
    star += "Z";
    vec![
        Case { path: tri.clone(), limit: 4.0 },
        Case { path: star, limit: 4.0 },
        Case { path: "M 50 200 L 120 60 L 190 200".into(), limit: 4.0 },
        Case { path: tri, limit: 1.9 },
    ]
}

fn mask(path: &str, stroke: &Stroke) -> Vec<u8> {
    Mask::new(path).style(stroke).size(T, T).render().0
}

fn main() {
    let out = std::env::args().nth(1).expect("output .ppm path");
    let cases = cases();
    let w = T * cases.len() as u32;
    let mut img = vec![255u8; (w * T * 3) as usize];
    for (i, c) in cases.iter().enumerate() {
        let mut s = Stroke::new(20.0);
        s.join(Join::Miter).miter_limit(c.limit);
        let thick = mask(&c.path, &s);
        let thin = mask(&c.path, &Stroke::new(1.5));
        for y in 0..T {
            for x in 0..T {
                let m = (y * T + x) as usize;
                let (a, b) = (thick[m] as f32 / 255.0, thin[m] as f32 / 255.0);
                // Stroke in dark blue, centerline in red on top.
                let mut px = [255.0 * (1.0 - a) + 40.0 * a, 255.0 * (1.0 - a) + 70.0 * a, 255.0 * (1.0 - a) + 140.0 * a];
                px = [px[0] * (1.0 - b) + 230.0 * b, px[1] * (1.0 - b) + 40.0 * b, px[2] * (1.0 - b) + 40.0 * b];
                let o = ((y * w + i as u32 * T + x) * 3) as usize;
                img[o..o + 3].copy_from_slice(&px.map(|v| v as u8));
            }
        }
    }
    let mut f = std::fs::File::create(out).unwrap();
    write!(f, "P6\n{w} {T}\n255\n").unwrap();
    f.write_all(&img).unwrap();
}