Store images of people who you would like to recognize and the app, using these images, will classify those people. We don't need to modify the app/retrain any ML model to add more people ( subjects ) for classification
If you're ML developer, you might have heard about FaceNet, Google's state-of-the-art model for generating face embeddings. In this
project, we'll use the FaceNet model on Android and generate embeddings ( fixed size vectors ) which hold information of the face.
The accuracy of the face detection system ( with FaceNet ) may not have a considerable accuracy. As, under the hood, we are comparing angles between vectors, this model would not produce results with a very high accuracy.
So, the aim of the FaceNet model is to generate a 128 dimensional vector of a given face. It takes in an 160 * 160 RGB image and
outputs an array with 128 elements. How is it going to help us in our face recognition project?
Well, the FaceNet model generates similar face vectors for similar faces. Here, my the term "similar", we mean
the vectors which point out in the same direction. We calculate this similarity by measuring cosine of the angle between the two
given 128 dimensional vectors.
In this app, we'll generate two such vectors and find the similarity between them. The one which has the highest similarity is our
You can download the FaceNet Keras
.h5 file from this repo.
So, an user can store images in his/her device in a specific folder. If, for instance, the user wants the app to recognize
two people namely "Rahul" and "Neeta". So the user needs to store the images by creating two directories namely "Rahul" and "Neeta"
and store their images inside of these directories.
images -> Rahul -> image_rahul.png Neeta -> image_neeta.png
The app will then process these images and classify these people thereafter. For face recognition, Firebase MLKit is used which
fetches bounding boxes for all the faces present in the camera frame.
This is different from existing face recognition apps as the user does not programme the app in such to recognize only a
fixed number of persons. If a new person is to be recognized, the system ( app ) has to be modified to include the new person as
The app's working is described in the steps below. The corresponding code is present in the file written in brackets.
imagesfolder present in the internal storage. Next, parse all the images present within
imagesfolder and store
the names of sub directories within
images. For every image, collect bounding box coordinates ( as a
Rect) using Firebase ML
Kit. Crop the face from the image ( the one which was collected from user's storage ) using the bounding box coordinates.
Finally, we have a list of cropped
Bitmapof the faces present in the images. Next, feed the cropped
Bitmapto the FaceNet
model and get the embeddings ( as
FloatArray). Now, we create a
HashMap<String,FloatArray>object where we store the names of
the sub directories as keys and the embeddings as their corresponding values.
The above procedure is carried out only on the app's startup. The steps below will execute on each camera frame.
androidx.camera.core.ImageAnalysis, we construct a
FrameAnalyserclass which processes the camera frames. Now, for a
given frame, we first get the bounding box coordinates ( as a
Rect) of all the faces present in the frame. Crop the face from
the frame using these boxes.
- Feed the cropped faces to the FaceNet model to generate embeddings for them. Using cosine similarity, calculate the similarity
scores for all subjects ( which we stored earlier as
HashMap<String,FloatArray>). The one with highest similarity is
determined. The final output is then stored as a
Predictionand passed to the
BoundingBoxOverlaywhich draws boxes and