Can you learn to sing just by singing?
 

I play the piano often, and I want to learn to sing so I can play songs with vocals. If I follow the correct singing techniques (deep breaths, straight posture, relaxed jaw, etc..), and sing along to playing songs on the piano, can I learn to sing well at one point? I've been told I sing off-tone, but my voice itself has potential. How can I go about this?

Are there any online resources that can help me ?

Thanks!

Singing can only be learned through rigorous masturbation.

^ then I'm an opera star

Sure you can, altho, vocal training will help. Its often hard to tell if you're off-pitch or out of scale, sometimes recording yourself will help.

I taught myself how to sing backup harmonies by practicing singing to the Rolling Stones and Jason and the Scorchers, riding around in my car.

Most of the sining I have "learned" has been from belting out various favourite songs while in the shower.
and masturbating, that helps.

Yes and no. Practicing singing builds your vocal chords up and helps build muscle memory, but you won't necessarily pick up on the most effective techniques without training (although it's not impossible).