Patio Cover Question

Looking to add something like this to my patio. The dimensions would be 22’x12’. My question is, I wanted to put a header the entire 22’ as the middle would be smack right in front of sliding glass door. I’ve tried to do some research on header/column size but everyone just mentions loads and no calculations or references to do the math on it.

Any help to links on the equations or additional information would be great.

Thanks in advance