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OpenCV 3.x with Python By Example

You're reading from   OpenCV 3.x with Python By Example Make the most of OpenCV and Python to build applications for object recognition and augmented reality

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Product type Paperback
Published in Jan 2018
Publisher Packt
ISBN-13 9781788396905
Length 268 pages
Edition 2nd Edition
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Authors (2):
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Gabriel Garrido Calvo Gabriel Garrido Calvo
Author Profile Icon Gabriel Garrido Calvo
Gabriel Garrido Calvo
Prateek Joshi Prateek Joshi
Author Profile Icon Prateek Joshi
Prateek Joshi
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Toc

Table of Contents (17) Chapters Close

Title Page
Copyright and Credits
Contributors
Packt Upsell
Preface
1. Applying Geometric Transformations to Images FREE CHAPTER 2. Detecting Edges and Applying Image Filters 3. Cartoonizing an Image 4. Detecting and Tracking Different Body Parts 5. Extracting Features from an Image 6. Seam Carving 7. Detecting Shapes and Segmenting an Image 8. Object Tracking 9. Object Recognition 10. Augmented Reality 11. Machine Learning by an Artificial Neural Network 1. Other Books You May Enjoy

Detecting and tracking faces


OpenCV provides a nice face detection framework. We just need to load the cascade file and use it to detect the faces in an image. Let's see how to do it:

import cv2 
import numpy as np 
 
face_cascade = cv2.CascadeClassifier('./cascade_files/haarcascade_frontalface_alt.xml') 
 
cap = cv2.VideoCapture(0) 
scaling_factor = 0.5 
 
while True: 
    ret, frame = cap.read() 
    frame = cv2.resize(frame, None, fx=scaling_factor, 
 fy=scaling_factor, interpolation=cv2.INTER_AREA)
 
    face_rects = face_cascade.detectMultiScale(frame, scaleFactor=1.3, minNeighbors=3) 
    for (x,y,w,h) in face_rects: 
        cv2.rectangle(frame, (x,y), (x+w,y+h), (0,255,0), 3) 
 
    cv2.imshow('Face Detector', frame) 
 
    c = cv2.waitKey(1) 
    if c == 27: 
        break 
 
cap.release() 
cv2.destroyAllWindows()

If you run the preceding code, the result will look something like the following image:

Understanding it better

We need a classifier model that can be used to detect faces...

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