Building a face detector application

In this section, we discuss how human faces can be detected from webcam images. A USB webcam needs to be connected to Raspberry Pi 3 to implement real-time human face detection.

How to do it...

1. Import the necessary packages:

import cv2 
import numpy as np 

2. Load the face cascade file:

frontalface_cascade= cv2.CascadeClassifier('haarcascade_frontalface_alt.xml') 

3. Check whether the face cascade file has been loaded:

if frontalface_cascade.empty(): 
  raiseIOError('Unable to load the face cascade classifier xml file') 

4. Initialize the video capture object:

capture = cv2.VideoCapture(0) 

5. Define the scaling factor:

scale_factor = 0.5 

6. Perform the operation until the Esc key is pressed:

# Loop until you hit the Esc key 
while True: 

7. Capture the current frame and resize it:

  ret, frame = capture.read() 
  frame = cv2.resize(frame, None, fx=scale_factor, fy=scale_factor,  
            interpolation=cv2.INTER_AREA) 

8. Convert the image frame into grayscale:

  gray_image = cv2.cvtColor...