How to create a thread to take a picture after 3 seconds?

Question

I've created a class to display my webcam video on a Tkinter screen and I would like to take 3 pictures(waiting 3 seconds after each picture taken) after a Tkinter button is pressed.

Here is my code(reduced), and my logic to take picture is done. Should I use Threads to solve this? I'm new to Python.

import tkinter, cv2, time, dlib, numpy as np, time, threading
from PIL import Image, ImageTk

class Tela:
def __init__(self, janela):
    self.janela = janela
    self.janela.title("Reconhecimento Facial")
    self.janela.config(background="#FFFFFF")
    self.image = None

    self.cam = cv2.VideoCapture(0)
    self.detector = dlib.get_frontal_face_detector()

    self.delay = 15
    self.update()
    self.janela.mainloop()

def update(self): # display image on gui
    ret, frame = self.cam.read()
    if ret:
        faces, confianca, idx = self.detector.run(frame)
        for i, face in enumerate(faces):
            e, t, d, b = (int(face.left()), int(face.top()), int(face.right()), int(face.bottom()))
            cv2.rectangle(frame, (e, t), (d, b), (0, 255, 255), 2)
        cv2image = cv2.cvtColor(frame, cv2.COLOR_BGR2RGBA)
        self.image = Image.fromarray(cv2image)
        imgtk = ImageTk.PhotoImage(image=self.image)
        self.painel.imgtk = imgtk
        self.painel.config(image=imgtk)
        self.janela.after(self.delay, self.update)

def take_picture(self):
    cou = 1  # counter of pictures
    start = time.clock()  # starts the time
    ret, frame = self.cam.read()
    if ret:
        faces, confianca, idx = self.detector.run(frame)
        secs = (time.clock() - start)  # count seconds
        for i, face in enumerate(faces):
            e, t, d, b = (int(face.left()), int(face.top()), int(face.right()), int(face.bottom()))
            cv2.rectangle(frame, (e, t), (d, b), (0, 255, 255), 2)
            if secs > 3:
                imgfinal = cv2.resize(frame, (750, 600))
                cv2.imwrite("fotos/pessoa." + str(id[0][0]) + "." + str(cou) + ".jpg", imgfinal)
                print("Foto " + str(cou) + " tirada")
                cou += 1
                start = time.clock()  # reset the counter of seconds
        if cou > 3:
            # here is where the thread should stop


     # Creates the window
     Tela(tkinter.Tk())

Mahmoud Elshahat · Accepted Answer · 2019-04-22T14:17:03.570

using time.sleep() will freeze your gui, with tkinter you can use after() which will call your method after x seconds, below is an example of how to call a function 4 times every 2 seconds, and you can use this idea in your application

import tkinter as tk

class App():
    def __init__(self):
        self.root = tk.Tk()
        self.label = tk.Label(text="Anything")
        self.label.pack()

        self.counter = 0
        self.take_picture(repeates=4, seconds=2)  # our desired function

        self.root.mainloop()


    def take_picture(self, repeates=0, seconds=1):
        if repeates:
            self.counter = repeates

        if self.counter == 0:
            print('no more execution')
            self.label.configure(text='Done, no more execution')
            return

        # doing stuff    
        text = f'function counting down # {self.counter}'
        self.label.configure(text=text)

        # schedule another call to this func using after()
        self.root.after(seconds * 1000, self.take_picture, 0, seconds)
        self.counter -= 1  # our tracker

app=App()

credits to this answer

score 0 · Answer 2 · answered Apr 18 '19 at 23:23

0

You should use time.sleep(). It takes an integer as an parameter and waits that many seconds and then the code resumes running.

answered Apr 18 '19 at 23:23

Q Paul

101
2

I tried to use time.sleep inside my take_picture method, the screen freezes though. – Bruno Ienne Apr 19 '19 at 15:00
So did it get stuck entirely or did it continue working after the three seconds? – Q Paul Apr 19 '19 at 15:15
Continue working after three seconds. Should I call a thread for this task? If so, how can I do it? – Bruno Ienne Apr 19 '19 at 15:19
I would think that `time.sleep()` is sufficient for adding a delay. – Q Paul Apr 19 '19 at 15:23
The time.sleep() function is stopping the whole program. I'll try to use 2 threads. One for updating screen and other for taking pictures – Bruno Ienne Apr 19 '19 at 16:14
Oh, sorry I didn't know that you needed the rest of the program to continue running while adding the delay. – Q Paul Apr 19 '19 at 18:13

How to create a thread to take a picture after 3 seconds?

2 Answers2