Function luminosity_blend_serial 

pub fn luminosity_blend_serial(
    backdrop_rgb: ArrayView3<'_, f32>,
    luminosity: ArrayView2<'_, f32>,
    out: &mut Array3<f32>,
)

Luminosity blend, single-threaded.

Same arguments, output and panics as luminosity_blend_core, but always runs serially. Public for benchmarking only (see module docs).