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.
With the multiple register writing code, the image quality is much
better. It's trivially easy to get a match score of 100, and 200 is
possible with a little effort. Remove the lowered match threshold.
Instead of writing each register in a separate USB transaction, we now
write up to 16 at once.
This drastically improves scan image quality due to reducing the amount of
time needed per iteration of the sampling loop (sending 1 USB transaction
per iteration instead of 7).
aes2501 can be mounted 180 degrees rotated (this happens on most part of
laptops), so driver should detect whether sensor is 180degrees rotated
and assemble frames in right order.
This driver works quite nicely. Seems a little too sensitive though (too
much black in the standardized image, not enough ridge gap definition).
Processing results are quite good, but you need a good enrollment image
(i.e. long!). It's best to get such images by pressing harder than you
might think necessary and swiping slowly.
