sclass CachedPosterizer is IPosterizer {
  IPosterizer posterizer;
  int[] cache;

  *(IPosterizer *posterizer) {
    makeCache();
  }
  
  // 0..255 to 0..255
  public int get(int brightness) {
    ret cache[brightness];
  }
  
  void makeCache {
    cache = new int[256];
    for brightness to 256:
      cache[brightness] = posterizer.get(brightness);
  }
}