Hi Alan, On Fri, 2016-09-23 at 14:23 -0400, Alan Davidson wrote: > Hi libfprint folks - > > I've got a U.are.U 4500 reader. I see in libfprint/drivers/uru4000.c > that the image dimensions are hardcoded to 290x384 pixels. However, > that doesn't appear to be the right aspect ratio for my hardware. > Running fprint_demo, I can see 5 scans side-by-side by enrolling a > print. If I rotate my finger 90 degrees between these scans, I see > that the horizontal axis is stretched out compared to the vertical > one (features that are left-to-right of each other in one image are > noticeably further apart than those same features in another image > where they're up-and-down). If I enroll my finger vertically and then > scan it sideways, the scans don't match. >
I think this is what is mentioned on the (rather old) URU4000 drivers ( https://www.freedesktop.org/wiki/Software/fprint/libfprint/uru4000/) page, which also mentions some anti distortion code to deal with this. However isn't this a rather "thought up" issue, as the unit really seems meant to be used in one direction only. I would however think it would make a (small?) difference in minutiae detection if the finger is not placed straight in the oval direction of the sensor pad. > I've also been using the closed source drivers from DigitalPersona > themselves, which do not have this problem: the distances between > corresponding minutiae don't vary as I rotate my finger, and it has > no trouble matching fingers that have been rotated. I believe the DP > drivers think the resolution of the reader is 354x391 (found by > comparing the bytes it records when you save fingerprints to a file > with Slide 10 of [1]). > > Has anyone else seen this? Is there a way to query the hardware to > see what resolution images it thinks it records? How can I adjust the > libfprint scans so they match fingerprints regardless of orientation? > I am using the unit without issues in a 1:n scenario. I must admit I have not tried rotating my finger. Question is if one could find the anti-distortion code mentioned (or if it is already there, I have not gone through the git history). Regards, Martin _______________________________________________ fprint mailing list [email protected] https://lists.freedesktop.org/mailman/listinfo/fprint
