interface IImageRegion<Img extends WidthAndHeight> {
  // REQUIRED METHODS
  
  // smallest rectangle that all of the region's pixels are contained in
  public Rect bounds();

  public ItIt<Pt> pixelIterator();
  public bool contains(int x, int y);
  
  // convenience methods
  
  public default bool contains(Pt p) { ret contains(p.x, p.y); }
  
  // OPTIONAL METHODS
  
  // get whole image that the region refers to
  public default Img image() { null; }
  
  // which object made this
  public default O creator() { null; }
  
  public default int indexInCreator() { ret 0; }
  
  // was diagonal walking enabled?
  public default Bool createdWithDiagonals() { null; }
  
  public default int numberOfPixels() { ret l(pixelIterator()); }
  public default Pt firstPixel() { ret first(pixelIterator()); }
  
  // gets the region's color (what exactly this means is defined
  // by the creator)
  public default RGB color() { null; }
  
  public default int brightness() { ret -1; }
  
  public default OnePathWithOrigin outline() {
    ret g22_regionOutline(this);
  }
}