This page details problems and experiences with NBIS, the fingerprint image processing included with libfprint.

MINDTCT pixels-per-mm (PPMM) parameter not obeyed

The ippmm parameter to get_minutiae() appears to be ignored, at least it's value does not make any difference to the resultant minutiae.

MINDTCT problems working with small images

The images from the AES4000 are 96x96 pixels, covering a small sensor area only. MINDTCTs enhancement code really makes a mess of the ridges, so much that most ridge information is lost and all detected minutiae are invalid. Using a standard image resize algorithm to scale the image to 200% or 300% in size results in proper results. Ideally MINDTCT would use the PPMM parameter to configure the image enhancement algorithms.

Bozorth3 matching

Bozorth3 match scores are loosely defined to be related to the number of matched minutiae, with 40 as a suggested match threshold.

It would be nice if bozorth3 produced a proportional response instead, based on the number of minutiae in the input images or something like that. For example, with aes4000 images, we generally get 10-20 minutiae making a match score of 40 quite hard to reach except with really good scans.