#!/usr/bin/env python

import cv2

import numpy as np

import datetime

import time

import io

import picamera

import sys

import os

import subprocess

## frame_diff finds two absolute differences between image matrices;

## 3 images are used to create a moving average of frames

def frame_diff(f0, f1, f2):

return result

## write_video changes the camera's resolution to 1280x720 for recording purposes,

## records for 30 seconds, then switches back to a lower resolution to check for motion again

def write_video(camera):

camera.resolution = (320,240)

print 'INITIALIZING MOTION DETECTION CAMERA'

camera = picamera.PiCamera()

camera.resolution = (320,240) # low resolution for frame comparison helps compensate for the RPi's CPU

camera.LED = False

stream = io.BytesIO()

threshold = 35 # Minimum pixel value change

min_pixel_change = 1000 # Minimum number of pixels changed

# initialize the first 3 frames before executing the loop

stream.seek(0)

camera.capture(stream, 'jpeg', True)

prev_frame = cv2.cvtColor((cv2.imdecode((np.fromstring(stream.getvalue(), dtype=np.uint8)), 1)), cv2.COLOR_BGR2GRAY)

stream.seek(0)

camera.capture(stream, 'jpeg', True)

current_frame = cv2.cvtColor((cv2.imdecode((np.fromstring(stream.getvalue(), dtype=np.uint8)), 1)), cv2.COLOR_BGR2GRAY)

stream.seek(0)

camera.capture(stream, 'jpeg', True)

next_frame = cv2.cvtColor((cv2.imdecode((np.fromstring(stream.getvalue(), dtype=np.uint8)), 1)), cv2.COLOR_BGR2GRAY)

print 'MOTION DETECTION ACTIVATED'

while True:

movement = frame_diff(prev_frame, current_frame, next_frame)

nonZero = cv2.countNonZero(movement) # counts the number of nonZero pixels - white pixels

if nonZero > min_pixel_change: # compares the number of changed pixels (white) to the threshold for minimum pixels changed

write_video(camera)

#subprocess will check disk space and delete old footage if necessary

subprocess.Popen([sys.executable, '/home/pi/motion_camera/disk_check.py'])

stream.seek(0)

camera.capture(stream, 'jpeg', True)

current_frame = cv2.cvtColor((cv2.imdecode((np.fromstring(stream.getvalue(), dtype=np.uint8)), 1)), cv2.COLOR_BGR2GRAY)

stream.seek(0)

camera.capture(stream, 'jpeg', True)

next_frame = cv2.cvtColor((cv2.imdecode((np.fromstring(stream.getvalue(), dtype=np.uint8)), 1)), cv2.COLOR_BGR2GRAY)

# move frames forward

prev_frame = current_frame

current_frame = next_frame

stream.seek(0)

camera.capture(stream, 'jpeg', True)

next_frame = cv2.cvtColor((cv2.imdecode((np.fromstring(stream.getvalue(), dtype=np.uint8)), 1)), cv2.COLOR_BGR2GRAY)

key= cv2.waitKey(10)

if key == 27:

cv2.destroyAllWindows()

break

print "Goodbye"