This app is for demonstration and to assist in development (e.g. helps evaluate image quality). It's a little quirky and not complete (there's a TODO list in the README file). Right now it only offers verification against a previously-enrolled fingerprint.
Be aware that libfprint does not guarantee a stable ABI. So, fprint_demo may break if you upgrade libfprint in future without recompiling fprint_demo.
You must enroll a finger before you can use fprint_demo. Currently the only easy way to do this is to use the
enroll example from libfprint.