opencv while loops, going back to first loop

Question

I have a the following python code (and I'm using opencv3). What this code needs accomplish is to take a live stream of a generic camera, and then analyze a static picture (or frame). The problem that I have have, is that after exiting the second nested while loop, i can figure out how to go back to the initial loop (#1st loop).

The code should :

Take live stream press 'q' to capture frame and go to the next loop on this second loop: if 's' -after the images is analyzed- it should go back to the 1st loop. if 'esc' the program should be terminated.

I did tried the recursion method (def () ) but I run into another problem in which i couldn't figure out how to terminate the program.

import numpy as np
import cv2

cap = cv2.VideoCapture(0)
#Set LED brightness for camera
cap.set(cv2.CAP_PROP_BRIGHTNESS, 120)

#1st loop
while (True):

    #capture camera stream
    ret, frame = cap.read()
    cv2.imshow('live image', frame)
if cv2.waitKey(0) == ord('q'):

    cap.release()
    cv2.destroyAllWindows()
    pass
    print ('image alteration block')



    #2nd loop
    while (True):
        img = frame
        cv2.imshow('image',img)
        k = cv2.waitKey(0)
        if k == 27:         # wait for ESC key to exit and terminate progra,
            cv2.destroyAllWindows()
            break

        elif k == ord('s'): # wait for 's' key to save the image and go back to the live stream
            cv2.imwrite('messigray.png',img)
            print ('go back to the beginning')
            cv2.destroyAllWindows()
        continue  #NOT SURE WHAT TO DO HERE

Answer 1

You're not allowing the program to escape the second while loop. Use a different while condition in the second loop. Instead of while(True) use a boolean:

#2nd loop
    second=True 
    while (second):
        img = frame
        cv2.imshow('image',img)
        k = cv2.waitKey(0)
        if k == 27:         # wait for ESC key to exit and terminate progra,
            cv2.destroyAllWindows()
            break

        elif k == ord('s'):
            cv2.imwrite('messigray.png',img)
            print ('go back to the beginning')
            cv2.destroyAllWindows()
            #modify the loop condition
            second = False 
        continue

That should get you out of the second loop, relying on breaks is not always the best way to handle while loops.