sinterface Decolorizer {
  int toGrayScale(int rgb);
  
  srecord Red is Decolorizer {
    public int toGrayScale(int rgb) { ret (rgb >> 16) & 0xFF; }
  }
  
  srecord Green is Decolorizer {
    public int toGrayScale(int rgb) { ret (rgb >> 8) & 0xFF; }
  }
  
  srecord Blue is Decolorizer {
    public int toGrayScale(int rgb) { ret rgb & 0xFF; }
  }
  
  srecord Alpha is Decolorizer {
    public int toGrayScale(int rgb) { ret (rgb >> 24) & 0xFF; }
  }
  
  // just the average of the 3 channels
  srecord Simple is Decolorizer {
    public int toGrayScale(int rgb) {
      int r = (rgb >> 16) & 0xFF;
      int g = (rgb >> 8) & 0xFF;
      int b = rgb & 0xFF;
      ret (r+g+b+1)/3;
    }
  }
}