Don't consider the scan complete unless theres at least
MIN_ROWS recorded or very long blank read occurred.
Typical problem spot: one brief touch before starting the
actual scan. Happens most commonly if scan is started from
before the first joint resulting in a gap after the inital touch.
http://lists.reactivated.net/pipermail/fprint/2009-December/001406.html
Check all the drivers for one that'll drive our device in
question, and prefer ones that have a discover() method that runs
successfully to a driver without such a method.
This allow drivers to both reject devices (if 2 drivers handle
the same USB IDs), or a single driver to handle variants of the
same device (through the devtype out value of the discover method).
New DigitalPersona devices have a new firmware. We now use a search
scheme to find the encryption byte, by examining known locations
in the firmware until we find something that we recognise.
[dsd@gentoo.org: some trivial changes:
fixed some warnings
fixed fp_img memory leak on error
renamed endpoint constants (calling a bulk endpoint 'ctrl' is confusing,
as a control endpoint is something different)
]
After lot 713, Microsoft fingerprint readers changed. The new version
comes with a new USB product ID and a challenge-response authentication
scheme where the device challenges the authenticity of the driver.
An independent third party produced documentation on the computations
needed to convert a challenge into the correct response, and I then used
this documentation to produce a clean-room reimplementation of the
authentication scheme.
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.
I want to offer the ability for an application to view a binarized
version of a scanned print. This lead onto a few changes:
1. Store minutiae and binarized data inside fp_img
2. Move resize code to the capture path, it previously happened much
later.
3. Add fp_img_binarize() to return a new image in binarized form.
4. Add a BINARIZED_FORM flag to prevent an image being binarized again.
In future, it would be nice to be able to binarize without detecting
minutiae, but this involves some work on the NBIS interaction.
The UPEK TouchChip is an active capacitance imaging device with a
press-type sensor. It also has image storage capabilities which will
hopefully be accessible through libfprint in the near future.
This device can be found in the Samsung P35 laptop.
