code: public Coordinate transform(Coordinate coordinate, Matrix matrix) {
  		if (coordinate != null && matrix != null) {
  			double x = matrix.getXx() * coordinate.getX() + matrix.getXy() * coordinate.getY() + matrix.getDx();
  			double y = matrix.getYx() * coordinate.getX() + matrix.getYy() * coordinate.getY() + matrix.getDy();
  			return new Coordinate(x, y);
  		}
  		return null;
  	}
docs: Transform a single coordinate by a given <code>Matrix</code>.
  
  @param coordinate
  The coordinate to transform.
  @param matrix
  The transformation matrix.
  @return Returns a transformed coordinate, or null if one of the given parameters was null.