code: public int addControl( float x , float y ) {
  		Control c = controls.grow();
  		c.q.set(x,y);
  		setUndistorted(controls.size()-1,x,y);
  		return controls.size()-1;
  	}
docs: Adds a new control point at the specified location.  Initially the distorted and undistorted location will be
  set to the same
  
  @param x coordinate x-axis in image pixels
  @param y coordinate y-axis in image pixels
  @return Index of control point