@Contract(pure = true)
  private static float @NotNull [] YPbPr01(float @NotNull [] rgb) {
    // http://www.equasys.de/colorconversion.html
    return new float[]{
      (float)((  0.299 * rgb[0] + 0.587 * rgb[1] + 0.114 * rgb[2])/256),
      (float)(( -0.169 * rgb[0] - 0.331 * rgb[1] + 0.500 * rgb[2])/256),
      (float)((  0.500 * rgb[0] - 0.419 * rgb[1] - 0.081 * rgb[2])/256)
    };
  }
@Contract(pure = true)
  private static float @NotNull [] YPbPr01(float @NotNull [] rgb)