Simple - just modify the code in the tutorial so that instead of looping over all the faces in the database, it just takes in an image you specify and searches with that:
FImage face = ...; //you load the face you want to search with here
DoubleFV testFeature = eigen.extractFeature(face);
String bestPerson = null;
double minDistance = Double.MAX_VALUE;
for (final String person : features.keySet()) {
for (final DoubleFV fv : features.get(person)) {
double distance = fv.compare(testFeature, DoubleFVComparison.EUCLIDEAN);
if (distance < minDistance) {
minDistance = distance;
bestPerson = person;
}
}
}
System.out.println("Best Guess: " + bestPerson);