Medusa Fingerprint Scanner 2.6

In Scanner mode, which is the default, placing your finger under the rear camera (the app uses both the camera's zoom and light to get a good image of your finger), you will see the camera input to the right of the screen. Medusa will keep analyzing continuously the images taken by the camera, and when it considers that it could be a finger, it will extract the Fingerprints, and its corresponding Minutiae (fingerprint ridge endings and bifurcations, that are used to compare fingerprints), which will be shown to the left of the screen. Once you see the fingerprint on the left image of the screen, you can save it as the Template fingerprint, using the 'Template' button. If there is a Fingerprint Template saved previously, after extracting the Fingerprint and Minutiae of a new finger image, it will compare both and display PASS or FAIL, depending on whether both fingerprints match or not.

After each Fingerprint extraction, you can press the 'Save Image' button, which will save 3 images to the public Pictures/Medusa folder. These are the camera input image of your finger, the extracted Fingerprint ridges, and the Fingerprint with the Minutiae on top. You can visualize these images with Image Gallery, another App dealing with images, or with your computer connecting the phone to it.

Pressing the phone's Menu/Options button, you go to the Options screen, where you can setup Medusa as a Locker for the screen and/or phone start-up. Due to Android's API limitations, this is not intended to be a replacement for the PIN/Password/Pattern unlock built-in Android, but an additional security step.

After setting up Medusa Locker, you can keep using the Scanner as before. But after locking the screen and/or rebooting the phone (depending on the options choosen on the Options screen), you will be redirected to the Medusa Locker screen. This is the same than Medusa Scanner, but without any buttons and options. The only way to remove this screen is scanning your finger. After getting a PASS (fingerprint scanned matches the stored template), the Medusa Locker screen will disappear.

Using the phone's camera to extract the fingerprints is quite challenging, among other reasons due to the 3D nature of the finger. This would be simplified with a specific fingerprint sensor, where you press your finger against a surface. Nevertheless, Medusa manages to get good results, by using some special algorithms to deal with these constraints.

In order to get the best results, however, it is better to place the finger at the same position, orientation and distance than when the template was acquired. It is specially important to try to place your finger parallel to the phone surface, so that the camera gets a planar view of your finger as much as possible.

Before turning on the Locker at the Options screen, please play with the Scanner for a while, to make sure that you get PASS consistently most of the times you scan your finger. Once you setup the Locker, you will not be able to use your phone unless Medusa grants you a PASS, with a fingerprint match.

If you are getting false negatives (FAIL when it should be PASS), it could be either because you are not placing properly your finger to get a good match (so placing it in a different position, orientation and/or distance, but most probably with a different tilt, so that it is not parallel to the phone surface), but it could be also due to a bad template. You can change your template at any time you see a good fingerprint extracted within the Medusa Scanner screen, with the 'Template' button.

The screen shots shown have the finger and corresponding fingerprint images intentionally blurred.