sclass SinglePixelPosterizer is IPosterizer {
  int brightnessLevels;
  double factor1, factor2;
  settable double drift; // between -1 and 1, normally
  settable double antiDrift; // between -1 and 1
  
  *(int *brightnessLevels) {
    factor1 = doubleRatio(brightnessLevels, 256);
    factor2 = doubleRatio(255, brightnessLevels-1);
  }
  
  // 0..255 to 0..255
  public int get(int brightness) {
    var inner = brightness*factor1+drift;
    var posterized = ifloor(inner)+antiDrift;
    ret clampUByteInt(iround(posterized*factor2));
  }
  
  [stdEq]
}