Vector transformVector(Vector vector)

Source 

Vector transformVector(Vector vector) {

  var vx = vector.x.toDouble();
  var vy = vector.y.toDouble();
  var tx = vx * this.a + vy * this.c + this.tx;
  var ty = vx * this.b + vy * this.d + this.ty;

  return new Vector(tx, ty);
}