auto detect face and take a snapshot with opencv

Question

i'm working on face recognition project with my college. what i'm trying to take a snapshot and save it if the face is detected automatically before closing the webcam. what I have now is open cam and wait if face is detected and press "q" to take snapshot and save the image. Here is the code:

import numpy as np
import cv2
import time

#import the cascade for face detection
face_cascade = cv2.CascadeClassifier('haarcascade_frontalface_default.xml')



def TakeSnapshotAndSave():
    # access the webcam (every webcam has a number, the default is 0)
    cap = cv2.VideoCapture(0)

    while(True):
        # Capture frame-by-frame
        ret, frame = cap.read()

        # to detect faces in video
        gray = cv2.cvtColor(frame, cv2.COLOR_BGR2GRAY)
        faces = face_cascade.detectMultiScale(gray, 1.3, 5)

        for (x,y,w,h) in faces:
            cv2.rectangle(frame,(x,y),(x+w,y+h),(255,0,0),2)
            roi_gray = gray[y:y+h, x:x+w]
            roi_color = frame[y:y+h, x:x+w]

        x = 0
        y = 20
        text_color = (0,255,0)
        # write on the live stream video
        cv2.putText(frame, "Press q when ready", (x,y), cv2.FONT_HERSHEY_PLAIN, 1.0, text_color, thickness=2)


        # if you want to convert it to gray uncomment and display gray not fame
        #gray = cv2.cvtColor(frame, cv2.COLOR_BGR2GRAY)

        # Display the resulting frame
        cv2.imshow('frame',frame)
        # press the letter "q" to save the picture
        if cv2.waitKey(1) & 0xFF == ord('q'):
            # write the captured image with this name
            cv2.imwrite('try.jpg',frame)
            break

    # When everything done, release the capture
    cap.release()
    cv2.destroyAllWindows()


if __name__ == "__main__":
    TakeSnapshotAndSave()

thank you in advance

Answer 1

Perform imwrite() in the for (x,y,w,h) in faces: loop itself. If you use a constant filename, your last detected face will be saved and the rest will be overwritten

Answer 2

I adapted your code to save 10 images just for testing, if you want infinite photos, just change the while condition. So in your code you were overwriting the current image so I changed the string parameter so that it was possible to take lots of pictures.

import numpy as np
import cv2
import time

#import the cascade for face detection
face_cascade = cv2.CascadeClassifier('haarcascade_frontalface_default.xml')

def TakeSnapshotAndSave():
    # access the webcam (every webcam has a number, the default is 0)
    cap = cv2.VideoCapture(0)

    num = 0 
    while num<10:
        # Capture frame-by-frame
        ret, frame = cap.read()

        # to detect faces in video
        gray = cv2.cvtColor(frame, cv2.COLOR_BGR2GRAY)
        faces = face_cascade.detectMultiScale(gray, 1.3, 5)

        for (x,y,w,h) in faces:
            cv2.rectangle(frame,(x,y),(x+w,y+h),(255,0,0),2)
            roi_gray = gray[y:y+h, x:x+w]
            roi_color = frame[y:y+h, x:x+w]

        x = 0
        y = 20
        text_color = (0,255,0)

        cv2.imwrite('opencv'+str(num)+'.jpg',frame)
        num = num+1

    # When everything done, release the capture
    cap.release()
    cv2.destroyAllWindows()


if __name__ == "__main__":
    TakeSnapshotAndSave()