text: I tried to perform face recognition using OpenCV, but I don't know how to recognize the faces of multiple people.
  The sample image is a photograph of the faces of three people, but only the leftmost face is recognized.Corresponding source code
  What I triedWhat I tried
  import matplotlib.pyplot as plt import urllib.request as req import cv2 url = "destination url of sample image" req.url retrieve (url, "sample image.png") img = cv2.imread ("Sample image.png") img_gray = cv2.cvtColor (img, cv2.COLOR_BGR2RGB) url2 = "" req.urlretrieve (url2, "cascade.xml") cascade_file = "cascade.xml" cascade = cv2.CascadeClassifier (cascade_file) face_list = cascade.detectMultiScale (img_gray, minSize = (100, 100)) if len (face_list) == 0: print ("failure") quit () for (x, y, w, h) in face_list: print ("Face position =", x, y, w, h) red = (0, 0, 255) cv2.rectangle (img, (x, y,), (x + w, y + h), red, thickness = 10) cv2.imwrite ("sample image-face-detect.png", img) plt.imshow (cv2.cvtColor (img, cv2.COLOR_BGR2RGB)) plt.show ()
  I wondered if I could change the argument of the detectMultiScale method, but it didn't work.
  I thought about how to divide the image, but I thought it was not a good method because it would not be very versatile.
  I'm not sure how to recognize the faces of multiple people in one process.
  The execution environment is Google Colaboratory.
  - Answer # 1
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  I made the argument of the Minsize method smaller and it worked.
  It seems that if the face is small, the argument needs to be small for the image.