There are two problems with this approach. First is safety which is covered, second is longevity. Connecting LEDs to the mains is a very bad idea without any type of regulation. LEDs, especially anything using a blue die (Blue, white, pink, purple, sometimes green) or a UV die like you are using are very sensitive to surges and even to static electricity. When you connect to the mains without regulation (using a transformer or not) every surge is going to be passed through to your LEDs. You are proposing a Mains circuit to a rectifier (hopefully through a fuse and preferably an Isolation transformer if the wiring is exposed) to a resistor and then to the LEDs. This leads to problems.