Function heatmap_color

tools/bloom-diff/src/main.rs:240–250

Map a difference magnitude (0..1) to a false-color hot palette so small errors stay dark and big errors scream. Goes black → red → yellow → white, amplified so typical-tolerance errors (1-2%) are visible without manually setting a gain.

(magnitude: f32)

/// yellow → white, amplified so typical-tolerance errors (1-2%) are
/// visible without manually setting a gain.
fn heatmap_color(magnitude: f32) -> Rgb<u8> {
    let m = (magnitude * 16.0).clamp(0.0, 1.0);
    let r = (m * 3.0).clamp(0.0, 1.0);
    let g = ((m - 0.33) * 3.0).clamp(0.0, 1.0);
    let b = ((m - 0.66) * 3.0).clamp(0.0, 1.0);
    Rgb([
        (r * 255.0) as u8,
        (g * 255.0) as u8,
        (b * 255.0) as u8,
    ])
}

fn write_heatmap(
    reference: &[[f32; 3]],