message: Fix loss of brightness in the JPEG encoder
diff: @@ -805,9 +805,9 @@ fn rgb_to_ycbcr<P: Pixel>(pixel: P) -> (u8, u8, u8) {
  let g: f32 = g.to_f32().unwrap();
  let b: f32 = b.to_f32().unwrap();
  - let y = 65.481 / max * r + 128.553 / max * g + 24.933 / max * b;
  - let cb = -37.797 / max * r - 74.203 / max * g + 112.0 / max * b + 128.;
  - let cr = 112. / max * r - 93.786 / max * g - 18.214 / max * b + 128.;
  + let y = 76.245 / max * r + 149.685 / max * g + 29.07 / max * b;
  + let cb = -43.0185 / max * r - 84.4815 / max * g + 127.5 / max * b + 128.;
  + let cr = 127.5 / max * r - 106.7685 / max * g - 20.7315 / max * b + 128.;
  (y as u8, cb as u8, cr as u8)
  }
  