import subprocess
import RPi.GPIO as GPIO
import time
import datetime
import picamera

GPIO.setmode(GPIO.BCM)
GPIO.setup(21, GPIO.IN, pull_up_down=GPIO.PUD_UP)

def get_file_name_pic():
    return datetime.datetime.now().strftime("%Y-%m-%d_%H.%M.%S.jpg")

with picamera.PiCamera() as camera:
    while True:
        input_state = GPIO.input(21)
        if input_state == False:
            print('Taking Picture...')
            camera.capture('/home/pi/'+get_file_name_pic())
            time.sleep(2)