"invalid bounding box"

[weiying-chen]

Why is the following code producing "invalid bounding box"?

use ril::prelude::*;

fn main() -> ril::Result<()> {
    let mut image = Image::<Rgba>::open("sample.png")?;
    let (width, height) = image.dimensions();

    let vertices = vec![(50, 0), (100, 25), (100, 75), (50, 100), (0, 75), (0, 25)];

    let border = Border::<L>::new(L(255), 1);
    let hexagon = Polygon::from_vertices(vertices)
        .with_fill(L(255))
        .with_border(border);

    let mut mask = Image::new(width, height, L(0));

    mask.draw(&hexagon);
    image.mask_alpha(&mask);
    image.save_inferred("sample_hexagon.png")?;
    Ok(())
}

This error doesn't happen if you remove .with_border(border);.

By the way, this is sample.png: https://i.stack.imgur.com/hTIji.jpg. It's a png image of 1024 x 1024 pixels.