I have a database of eye images for which i have generated a feature vector database,now i am taking a query image as input and calculating its feature vector and comparing it with the feature vectors stored in the feature vector database.after compairson i am displaying the top 5 closest images.and now i want to write a code for calculating FAR and GAR. I dont have any idea about how i can do it. please just give me some hints so that i can do it myself.