method lerp

Source

static IconThemeData lerp(IconThemeData begin, IconThemeData end, double t) {
  return new IconThemeData(
    color: Color.lerp(begin.color, end.color, t),
    opacity: ui.lerpDouble(begin.opacity, end.opacity, t),
    size: ui.lerpDouble(begin.size, end.size, t)
  );
}