I think most QR code readers can handle reading at an angle, and calculate what angle they're at by the relative distances between the reference squares you'll

I think most QR code readers can handle reading at an angle, and calculate what angle they're at by the relative distances between the reference squares you'll see in three corners of the code. But telling the difference between a code that is angled on one dimension, and a code that is on a curve would be much more difficult to do reliably. in both cases, one dimension would be compressed, but in the case of the curve, the compression ration would vary.