Function render_mono8 

pub fn render_mono8(
    width: usize,
    height: usize,
    background: u8,
    blobs: &[(f64, f64)],
    peak: f64,
    sigma: f64,
) -> Vec<u8> 

Render a width x height Mono8 image: a flat background with an additive Gaussian blob (peak peak, standard deviation sigma pixels) at each (x, y) center in blobs. Stride equals width.

Only a window of a few sigma around each blob is touched, so this is cheap even for large images.