[fprint] AES 1610 support

[wxCover]

Daniel Drake wrote :
> wxCover wrote:
>> Well... I did it but I'm not sure it worked. I haven't received any 
>> confirmation or whatever. Should I retry?
>
> I just force-subscribed you. Let me know if there are any further 
> problems sending or receiving the list mail.
I've received the confirmation. It should work now! thanks
>> Well, I've spoke too soon in my last mail! I hadn't tried to enroll 
>> and verify. The images I get looks nice BUT for the moment, I have 
>> problems with enrollment and verification.
>> I think the main problem is that I'm not getting enough minutiae. 
>> Usually, for a fingerprint that looks really nice, I get something 
>> like 10~15 minutiae. And if the image is not perfect (very often), 
>> the number is less than 10.
>
> OK.
>
>> Now, speaking about verification, I haven't manage to get it to 
>> match. The scores are always low. I think this is due to the poor 
>> number of minutiae.
>> I don't know how to improve the situation. Is there some tweaking we 
>> can do with the algorithm which calculate minutiaes ?
>
> How low are the scores? Is there still a noticeable difference between 
> scores of matching and non-matching finger scans?
>
> The default match score is 40, but the resultant score is dependant on 
> the number of detected minutiae, so for small minutiae counts it is 
> hard to reach such values.
>
> The driver can lower the match score threshold via the bz3_threshold 
> attribute (e.g. aes4000 does this).
>
> You may also want to try enlarging the image with the enlarge_factor 
> attribute. Again, aes4000 does this as the binarization results were 
> horrible otherwise...
>
> The latest fprint_demo and libfprint from git will undoubtedly help 
> you get a better understanding of the problems here. You can view the 
> scanned image, the binarized image, and you can plot the detected 
> minutiae on both.
I've installed both from git and tested all that stuff.
There is a difference between the scores. I've changed bz3_threshold to 
15. With this setting, it works better: I get many more matches. I 
haven't seen any wrong positives with that. But there are some false 
negatives. Maybe we could lower bz3_threshold a bit more? When I read 
another finger than the one enrolled, I never get scores higher than 7. 
The maximum score I got was 32.
I've tried to change the enlarge factor but it didn't help (in fact, it 
may be worst=scores lower). Maybe because the binarization gives pretty 
good results (see the attached files)?
In my last mail, I told the number of minutiae was very often lower than 
10. In fact, now with "training", I'm getting much less "bad scan" errors...
In the attachments, you'll find 3 files:
-two with the correct finger (the one enrolled)
-one with another finger
bz_xx is for the score and min_xx is the number of minutiae.

In fact a big issue is to have a correct enrollment. I think in the 
future we'll need to read several times the same finger and see if 
there's no problem with it. Anyway, you may already know that!
>
> Thanks,
> Daniel
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