pub fn jfa_preprocess(target: &mut Rgba32FImage) {
    let (width, height) = target.dimensions();
    target.par_enumerate_pixels_mut().for_each(|(x, y, pixel)| {
        let uv = Vec2::new(x as f32 / width as f32, y as f32 / height as f32);
        pixel[2] = 0.;
        pixel[3] = 0.;
        if pixel[3] > 0.5 {
            // Inside
            pixel[0] = uv.x;
            pixel[1] = uv.y;
            pixel[3] = 1.;
        } else {
            // Outside
            pixel[0] = -uv.x;
            pixel[1] = -uv.y;
            pixel[3] = 1.;
        }
    });
}

pub fn jfa(src: &Rgba32FImage, dest: &mut Rgba32FImage, iteration: u32, width: u32, height: u32) {
    let step = (width.max(height) >> (iteration + 1)).max(1);
    let tex_fsize = Vec2::new(width as f32, height as f32);
    let tex_isize = IVec2::new(width as i32, height as i32);

    dest.par_enumerate_pixels_mut().for_each(|(x, y, pixel)| {
        let px = IVec2::new(x as i32, y as i32);
        let mut best_distance_sqr = f32::INFINITY;
        let mut best_uv = Vec2::ZERO;
        let is_inside = src.get_pixel(px.x as u32, px.y as u32)[0] > 0.;

        for mut dx in -1..=1 {
            dx *= step as i32;
            for mut dy in -1..=1 {
                dy *= step as i32;
                let neighbor_px = px + IVec2::new(dx, dy);
                if neighbor_px.x < 0
                    || neighbor_px.x >= tex_isize.x
                    || neighbor_px.y < 0
                    || neighbor_px.y >= tex_isize.y
                {
                    continue;
                }

                let neighbor_saved_px = src.get_pixel(neighbor_px.x as u32, neighbor_px.y as u32);
                if neighbor_saved_px[3] < 0.5 {
                    continue;
                }
                let mut neighbor_saved_px =
                    Vec2::new(neighbor_saved_px[0], neighbor_saved_px[1]) * tex_fsize;
                if !is_inside {
                    neighbor_saved_px = -neighbor_saved_px;
                }
                let distance = neighbor_saved_px.distance_squared(px.as_vec2());
                if distance < best_distance_sqr {
                    best_distance_sqr = distance;
                    best_uv = neighbor_saved_px / tex_fsize;
                }
            }
        }

        if is_inside {
            pixel[0] = best_uv.x;
            pixel[1] = best_uv.y;
        } else {
            pixel[0] = -best_uv.x;
            pixel[1] = -best_uv.y;
        }
    });
}