FingerprintImage.decode() returned null

I am trying to implement this library in an Android project. Everything’s done as explained in the Java tutorial. However, when trying to do the moment of truth, matching two fingerprint images, I get this error.

Following is the error I am getting

‌

Bitmap probeBm = BitmapFactory.decodeResource(getResources(), R.drawable.fingerprintblob);
Bitmap candidateBm = BitmapFactory.decodeResource(getResources(), R.drawable.fingerprintupload);

saveBitmapToFile(dir, "fingerprintblob.png", probeBm, Bitmap.CompressFormat.PNG, 100);
saveBitmapToFile(dir, "fingerprintupload.png", candidateBm, Bitmap.CompressFormat.PNG, 100);
byte[] probeImage = Files.readAllBytes(Paths.get(dir + File.separator + "fingerprintblob.png"));
byte[] candidateImage = Files.readAllBytes(Paths.get(dir + File.separator + "fingerprintupload.png"));

FingerprintTemplate candidate = new FingerprintTemplate(
        new FingerprintImage()
                .dpi(500)
                .decode(candidateImage)
);

FingerprintTemplate probe = new FingerprintTemplate(
        new FingerprintImage()
        .dpi(500)
        .decode(probeImage)
);

// now match
double score = new FingerprintMatcher()
        .index(probe)
        .match(candidate);

Log.d(TAG, "fingerprint match score " + score);

double threshold = 40;
boolean matches = score >= threshold;
Log.d(TAG, "fingerprint matches? " + matches);

And below is the error I am getting from stack trace print

‌

2019-11-20 10:53:35.310 12137-12137/com.vizcreations.biometrics E/AndroidRuntime: FATAL EXCEPTION: main
    Process: com.vizcreations.biometrics, PID: 12137
    java.lang.BootstrapMethodError: Exception from call site #52 bootstrap method
        at com.machinezoo.sourceafis.ImageDecoder.decodeAny(ImageDecoder.java:79)
        at com.machinezoo.sourceafis.FingerprintImage.decode(FingerprintImage.java:84)
        at com.vizcreations.biometrics.DashboardActivity.testMatchLocalFingerprints(DashboardActivity.java:1087)
        at com.vizcreations.biometrics.DashboardActivity.captureFingerprint(DashboardActivity.java:607)
        at com.vizcreations.biometrics.DashboardActivity.onDialogOptionSelected(DashboardActivity.java:563)
        at com.vizcreations.biometrics.fragment.SearchstudentDialogFragment$2.onClick(SearchstudentDialogFragment.java:55)
        at androidx.appcompat.app.AlertController$AlertParams$3.onItemClick(AlertController.java:1068)
        at android.widget.AdapterView.performItemClick(AdapterView.java:318)
        at android.widget.AbsListView.performItemClick(AbsListView.java:1198)
        at android.widget.AbsListView$PerformClick.run(AbsListView.java:3178)
        at android.widget.AbsListView$3.run(AbsListView.java:4132)
        at android.os.Handler.handleCallback(Handler.java:873)
        at android.os.Handler.dispatchMessage(Handler.java:99)
        at android.os.Looper.loop(Looper.java:201)
        at android.app.ActivityThread.main(ActivityThread.java:6810)
        at java.lang.reflect.Method.invoke(Native Method)
        at com.android.internal.os.RuntimeInit$MethodAndArgsCaller.run(RuntimeInit.java:547)
        at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:873)
     Caused by: java.lang.ClassCastException: Bootstrap method returned null
        at com.machinezoo.sourceafis.ImageDecoder.decodeAny(ImageDecoder.java:79) 
        at com.machinezoo.sourceafis.FingerprintImage.decode(FingerprintImage.java:84) 
        at com.vizcreations.biometrics.DashboardActivity.testMatchLocalFingerprints(DashboardActivity.java:1087) 
        at com.vizcreations.biometrics.DashboardActivity.captureFingerprint(DashboardActivity.java:607) 
        at com.vizcreations.biometrics.DashboardActivity.onDialogOptionSelected(DashboardActivity.java:563) 
        at com.vizcreations.biometrics.fragment.SearchstudentDialogFragment$2.onClick(SearchstudentDialogFragment.java:55) 
        at androidx.appcompat.app.AlertController$AlertParams$3.onItemClick(AlertController.java:1068) 
        at android.widget.AdapterView.performItemClick(AdapterView.java:318) 
        at android.widget.AbsListView.performItemClick(AbsListView.java:1198) 
        at android.widget.AbsListView$PerformClick.run(AbsListView.java:3178) 
        at android.widget.AbsListView$3.run(AbsListView.java:4132) 
        at android.os.Handler.handleCallback(Handler.java:873) 
        at android.os.Handler.dispatchMessage(Handler.java:99) 
        at android.os.Looper.loop(Looper.java:201) 
        at android.app.ActivityThread.main(ActivityThread.java:6810)

Seemed like I sent an empty image, but the byte count was greater than 0, so it’s not a null image. Only thing I can think of is that it may not be encoded with 500 dpi? I had originally converted the fingerprint to PNG image and save as BLOB to a MySQL database, then retrieve it back as image and downloaded it. The fingerprint I am matching with it is from a scanner again dumped as image before being converted to file and uploaded to a Node JS server from a byte[] array the scanner had outputted.

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