One Saturday morning, I was having a breakfast when I discovered the face_recognition project. I started to play with the OpenCV example — I put my picture in, and wow, it works like a charm! It was pretty straightforward in detecting my face, and I can also obtain facial landmarks. One landmark that I can get, for example, is the nose tip. Playing with this script, I realized that with the nose tip, I can determine the position of the face. I can see if my face is aligned to the center or if it is moved to one side. Additionally, I have a new IoT device (one ESP32), and I wanted to do something with it. Let's say, for example, I wanted to control a servo (SG90) and move it from left to right depending on my face's position.

First, we have the main Python script. With this script, I detect my face, the nose tip, and the position of my face. With this position, I will emit an event to an MQTT broker (a mosquitto server running on my laptop).

import face_recognition
import cv2
import numpy as np
import math
import paho.mqtt.client as mqtt
 
video_capture = cv2.VideoCapture(0)
 
gonzalo_image = face_recognition.load_image_file("gonzalo.png")
gonzalo_face_encoding = face_recognition.face_encodings(gonzalo_image)[0]
 
known_face_encodings = [
    gonzalo_face_encoding
]
known_face_names = [
    "Gonzalo"
]
 
RED = (0, 0, 255)
GREEN = (0, 255, 0)
BLUE = (255, 0, 0)
 
face_locations = []
face_encodings = []
face_names = []
process_this_frame = True
status = ''
labelColor = GREEN
 
client = mqtt.Client()
client.connect("localhost", 1883, 60)
 
while True:
    ret, frame = video_capture.read()
 
    # Resize frame of video to 1/4 size for faster face recognition processing
    small_frame = cv2.resize(frame, (0, 0), fx=0.25, fy=0.25)
 
    # Convert the image from BGR color (which OpenCV uses) to RGB color (which face_recognition uses)
    rgb_small_frame = small_frame[:, :, ::-1]
 
    face_locations = face_recognition.face_locations(rgb_small_frame)
    face_encodings = face_recognition.face_encodings(rgb_small_frame, face_locations)
    face_landmarks_list = face_recognition.face_landmarks(rgb_small_frame, face_locations)
 
    face_names = []
    for face_encoding, face_landmarks in zip(face_encodings, face_landmarks_list):
        matches = face_recognition.compare_faces(known_face_encodings, face_encoding)
        name = "Unknown"
 
        if True in matches:
            first_match_index = matches.index(True)
            name = known_face_names[first_match_index]
 
            nose_tip = face_landmarks['nose_tip']
            maxLandmark = max(nose_tip)
            minLandmark = min(nose_tip)
 
            diff = math.fabs(maxLandmark[1] - minLandmark[1])
            if diff < 2:
                status = "center"
                labelColor = BLUE
                client.publish("/face/{}/center".format(name), "1")
            elif maxLandmark[1] > minLandmark[1]:
                status = ">>>>"
                labelColor = RED
                client.publish("/face/{}/left".format(name), "1")
            else:
                status = "<<<<"
                client.publish("/face/{}/right".format(name), "1")
                labelColor = RED
 
            shape = np.array(face_landmarks['nose_bridge'], np.int32)
            cv2.polylines(frame, [shape.reshape((-1, 1, 2)) * 4], True, (0, 255, 255))
            cv2.fillPoly(frame, [shape.reshape((-1, 1, 2)) * 4], GREEN)
 
        face_names.append("{} {}".format(name, status))
 
    for (top, right, bottom, left), name in zip(face_locations, face_names):
        # Scale back up face locations since the frame we detected in was scaled to 1/4 size
        top *= 4
        right *= 4
        bottom *= 4
        left *= 4
 
        if 'Unknown' not in name.split(' '):
            cv2.rectangle(frame, (left, top), (right, bottom), labelColor, 2)
            cv2.rectangle(frame, (left, bottom - 35), (right, bottom), labelColor, cv2.FILLED)
            cv2.putText(frame, name, (left + 6, bottom - 6), cv2.FONT_HERSHEY_DUPLEX, 1.0, (255, 255, 255), 1)
        else:
            cv2.rectangle(frame, (left, top), (right, bottom), BLUE, 2)
 
    cv2.imshow('Video', frame)
 
    if cv2.waitKey(1) & 0xFF == ord('q'):
        break
 
video_capture.release()
cv2.destroyAllWindows()

Now another Python script will be listening to MQTT events and will trigger one event with the position of the servo. I know that this second Python script may be unnecessary. We can move its logic to the ESP32 and main OpenCV script, but I was playing with MQTT and I wanted to decouple it a little bit.

import paho.mqtt.client as mqtt
 
class Iot:
    _state = None
    _client = None
    _dict = {
        'left': 0,
        'center': 1,
        'right': 2
    }
 
    def __init__(self, client):
        self._client = client
 
    def emit(self, name, event):
        if event != self._state:
            self._state = event
            self._client.publish("/servo", self._dict[event])
            print("emit /servo envent with value {} - {}".format(self._dict[event], name))
 
 
def on_message(topic, iot):
    data = topic.split("/")
    name = data[2]
    action = data[3]
    iot.emit(name, action)
 
 
client = mqtt.Client()
iot = Iot(client)
 
client.on_connect = lambda self, mosq, obj, rc: self.subscribe("/face/#")
client.on_message = lambda client, userdata, msg: on_message(msg.topic, iot)
 
client.connect("localhost", 1883, 60)
client.loop_forever()

And finally the ESP32. Here, we will connect to my Wi-Fi and my MQTT broker.

#include <WiFi.h>
#include <PubSubClient.h>
 
#define LED0 17
#define LED1 18
#define LED2 19
#define SERVO_PIN 5
 
// wifi configuration
const char* ssid = "my_ssid";
const char* password = "my_wifi_password";
// mqtt configuration
const char* server = "192.168.1.111"; // mqtt broker ip
const char* topic = "/servo";
const char* clientName = "com.gonzalo123.esp32";
 
int channel = 1;
int hz = 50;
int depth = 16;
 
WiFiClient wifiClient;
PubSubClient client(wifiClient);
 
void wifiConnect() {
  Serial.print("Connecting to ");
  Serial.println(ssid);
 
  WiFi.begin(ssid, password);
 
  while (WiFi.status() != WL_CONNECTED) {
    delay(500);
    Serial.print("*");
  }
 
  Serial.print("WiFi connected: ");
  Serial.println(WiFi.localIP());
}
 
void mqttReConnect() {
  while (!client.connected()) {
    Serial.print("Attempting MQTT connection...");
    if (client.connect(clientName)) {
      Serial.println("connected");
      client.subscribe(topic);
    } else {
      Serial.print("failed, rc=");
      Serial.print(client.state());
      Serial.println(" try again in 5 seconds");
      delay(5000);
    }
  }
}
 
void callback(char* topic, byte* payload, unsigned int length) {
  Serial.print("Message arrived [");
  Serial.print(topic);
 
  String data;
  for (int i = 0; i < length; i++) {
    data += (char)payload[i];
  }
 
  int value = data.toInt();
  cleanLeds();
  switch (value)  {
    case 0:
      ledcWrite(1, 3400);
      digitalWrite(LED0, HIGH);
      break;
    case 1:
      ledcWrite(1, 4900);
      digitalWrite(LED1, HIGH);
      break;
    case 2:
      ledcWrite(1, 6400);
      digitalWrite(LED2, HIGH);
      break;
  }
  Serial.print("] value:");
  Serial.println((int) value);
}
 
void cleanLeds() {
  digitalWrite(LED0, LOW);
  digitalWrite(LED1, LOW);
  digitalWrite(LED2, LOW);
}
 
void setup() {
  Serial.begin(115200);
 
  ledcSetup(channel, hz, depth);
  ledcAttachPin(SERVO_PIN, channel);
 
  pinMode(LED0, OUTPUT);
  pinMode(LED1, OUTPUT);
  pinMode(LED2, OUTPUT);
  cleanLeds();
  wifiConnect();
  client.setServer(server, 1883);
  client.setCallback(callback);
 
  delay(1500);
}
 
void loop()
{
  if (!client.connected()) {
    mqttReConnect();
  }
 
  client.loop();
  delay(100);
}

Here is a video with the working prototype in action:

The source code is available in my GitHub account.