[fprint] Merging together multiple scans of the same fingerprint?

[Vasily Khoruzhick]

Hi Alan,

On Thu, Aug 11, 2016 at 10:03 AM, Alan Davidson <alan at key.me> wrote:
> Hi libfprint folks -
>
> I've got a Digital Persona U.are.U 4500 fingerprint reader, and I'm trying
> to migrate to libfprint from the closed source drivers I got from Digital
> Persona themselves.
>
> The driver chosen by libfprint is uru4000, which seems right. When I call
> fp_dev_get_nr_enroll_stages on the device, it returns 1: a single scan is
> enough to enroll a fingerprint. and indeed, I can scan my finger once and
> get back a fp_print_data struct (through the callback passed to
> fp_async_enroll_start).

Probably you're using old libfprint. Newer returns 5. It scans finger
5 times and upon verification
it compares scanned finger to a gallery.

> However, the old closed source drivers had a way to capture a set of 4 scans
> of the same finger (what they called an "enrollment", as opposed to a
> single-scan "capture") that were merged together to form a more robust,
> reliable view of the finger. Is there a way to mirror that functionality
> with libfprint, given that my device seems to use just 1 stage for an
> enrollment?

Stitching images together is not implemented.

> The motivation here is that when someone registers their fingerprint, we
> want to make sure we've got a high quality scan on file, so that they can
> reliably match it later.
>
> Thanks in advance for your help.

Regards,
Vasily

>  - Alan
>
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