persistable asclass AbstractSSI {
  // Color in 15 bit
  settable short hi15color;
  
  Color color() {
    ret main hi15color(hi15color);
  }
  
  selfType color(RGB color) {
    ret hi15color(rgbToHi15(color));
  }
  
  abstract SSI toSSI aka render();
  
  void copyAbstractSSI(AbstractSSI dest) {
    dest.hi15color(hi15color);
  }
  
  // size estimate after compression
  abstract int sizeInInts();
}