sclass SinglePixelPosterizer is IPosterizer {
  int brightnessLevels;
  double factor1, factor2;
  
  *(int *brightnessLevels) {
    factor1 = doubleRatio(brightnessLevels, 256);
    factor2 = doubleRatio(255, brightnessLevels-1);
  }
  
  // 0..255 to 0..255
  public int get(int brightness) {
    ret iround(ifloor(brightness*factor1)*factor2);
  }
}