Some scanners provide hardware assistance in frame assemling, i.e.
horizontal and vertical offset to previous frame is provided. This
commit improves code to utilise that assistance. Sensors without
hardware assistance will use software algorithm, which was also
improved to do search in horizontal direction.
ID is just a some magic number to make fingerprint from one scanner model
incompatible with another scanner model. Get rid of "magic", declare enum
and use it.
https://bugs.freedesktop.org/show_bug.cgi?id=56956
bz threshold is now 10 (instead of 15). I think it is ok for the moment.
If we manage to get higher image quality in the future, we'll change that.
max_frame is set to 350. 150 was too low => incomplete fingerprints
the driver was designed to stop the acquisition as soon as it gets a blank
frame (=> incomplete fingerprints). Now it waits to have at least 50 blank
frames before stopping.
This is an active capacitance swipe-type device similar to but smaller
than the AES2501.
Image processing performance is good but matching performance is not so
good. The bozorth3 matcher needs tweaking in order to better cope with
small sets of minutiae.
With a lowered threshold, matching performance is good enough for now.
