Face Detection

1. Course Content

• Run example programs, use the mediapipe framework to detect faces.

2. Program Startup

For Raspberry Pi 5 users, if the ROS container is not started, you need to start the container first,

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bringup_m3

Open a terminal inside the container,

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exec_m3

• Run face detection node in terminal

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ros2 launch m3_bringup mediapipe_demo.launch.py demo:=FaceDetector

After the program runs, as shown in the figure below, detected faces will be boxed and the detection score will be displayed. The higher the score, the more likely it is recognized as a face.

3. Core Code Analysis

Program code path:

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~/yahboomM3_ws/code_ws/src/m3_common_demo/m3_common_demo/mediapipe/05_FaceDetection.py

Import the required library files

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import time
import cv2 as cv
import numpy as np
import rclpy
from rclpy.node import Node
#import mediapipe library
import mediapipe as mp
from cv_bridge import CvBridge
from sensor_msgs.msg import Image
from arm_msgs.msg import ArmJoints
import cv2

Initialize data and define publishers and subscribers,

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def __init__(self, name):
    super().__init__(name)
    self.minDetectionCon=0.5
    #Use the class in the mediapipe library to define a face detection object
    self.mpFaceDetection = mp.solutions.face_detection
    self.mpDraw = mp.solutions.drawing_utils
    self.facedetection = self.mpFaceDetection.FaceDetection(min_detection_confidence=self.minDetectionCon)
    self.rgb_bridge = CvBridge()
​
    #Define the subscriber for color image topic
    self.sub_rgb = self.create_subscription(Image,"/camera/color/image_raw",self.get_RGBImageCallBack,100)

Color image callback function,

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def get_RGBImageCallBack(self,msg):
    #Use CvBridge to convert color image message data to image data
    rgb_image = self.rgb_bridge.imgmsg_to_cv2(msg, "bgr8")
    #Pass the obtained image to the defined findFaces function for face detection program
    frame,_ = self.findFaces(rgb_image)
    key = cv2.waitKey(1)
    cv.imshow('frame', frame)

findFaces function,

 3D Object Recognition
Gesture Recognition