CODA BAR format
I keep a bar code for the library on my bicycle helmet so that it is always with me.
I studied the one on my card, and guessed that the Sonoma county library uses CODA BAR (NW7) with start char B and stop char C
My printer software "P-Touch Editor" does not seem to be able to generate these, so I use http://generator.onbarcode.com/online-codabar-barcode-generator.aspx to generate a PNG which I can then print.
I don't ride my bike to the Marin or Woodland libraries often enough to carry them up there.