Canvas Fingerprinting: fonts

As I know, TBB blocks ctx.getImageData. But I think it is not enough. Look at this. https://web.archive.org/web/20141016035848/https://gist.github.com/KOLANICH/00b9145743d841cff4d7 I tried this, the fingerprint survives restart of TBB. I don't know, wheither this fingerprint can be used to identify user's OS (at least it can be used to identify fonts) and hardware, but it is differen than the one generated with the browser in the OS.