message: Update decoder to be correct for all colors.
diff: @@ -88,19 +88,19 @@ fn cmyk_to_rgb(input: &[u8]) -> Vec<u8> {
  let size = input.len() - input.len() / 4;
  let mut output = Vec::with_capacity(size);
  + let inv = 1.0 / 255.0;
  for pixel in input.chunks(4) {
  let c = f32::from(pixel[0]);
  let m = f32::from(pixel[1]);
  let y = f32::from(pixel[2]);
  let k = 255.0 - f32::from(pixel[3]);
  - let k_sub = k / 255.0;
  -
  + let k_sub = -k;
  + let k = k * 255.0;
  // CMY -> RGB
  - let r = k - c * k_sub;
  - let g = k - m * k_sub;
  - let b = k - y * k_sub;
  -
  + let r = (c * k_sub + k) * inv;
  + let g = (y * k_sub + k) * inv;
  + let b = (m * k_sub + k) * inv;
  output.push(r as u8);
  output.push(g as u8);
  